feat(ui): show the session title in the header bar (#340)

Fixes #299

## Summary
- show the active session title in the instance header, just after the
menu switch.
- keep the title visible whenever the left session drawer is not pinned,
using a quiet two-line header treatment without active-item
highlighting.
- when the unpinned drawer is open as a floating overlay, keep the title
in the same left header slot so the drawer covers it instead of pushing
toolbar controls around.
- disable the feature in mobile view

## Validation
- `git diff --check`
- `npm run typecheck --workspace @codenomad/ui`
- `npm run build --workspace @codenomad/ui`
- visually validated in the rebuilt desktop app raw executable

packages/ui/src/App.tsx

@@ -103,7 +103,6 @@ const App: Component = () => {
     binaryPath: string
     instanceId: string
   } | null>(null)
-
   const phoneQuery = useMediaQuery("(max-width: 767px)")
   const isPhoneLayout = createMemo(() => phoneQuery())
 

packages/ui/src/components/instance/instance-shell2.tsx

@@ -514,6 +514,23 @@ const InstanceShell2: Component<InstanceShellProps> = (props) => {
     </div>
   )
 
+  const renderPreviewToggleButton = () => (
+    <Show when={!showingInfoView()}>
+      <IconButton
+        color="inherit"
+        onClick={handlePreviewButtonClick}
+        aria-label={previewToggleLabel()}
+        title={previewToggleLabel()}
+        size="small"
+      >
+        {(() => {
+          const Icon = PreviewToggleIcon()
+          return <Icon class="w-5 h-5" aria-hidden="true" />
+        })()}
+      </IconButton>
+    </Show>
+  )
+
   const handleCommandPaletteClick = () => {
     showCommandPalette(props.instance.id)
   }
@@ -834,6 +851,50 @@ const InstanceShell2: Component<InstanceShellProps> = (props) => {
   }
 
   const showingInfoView = createMemo(() => activeSessionIdForInstance() === "info")
+  const activeSessionTitle = createMemo(() => {
+    if (showingInfoView()) return null
+    const title = activeSessionForInstance()?.title?.trim()
+    return title || t("sessionList.session.untitled")
+  })
+  const showHeaderLeftSlot = createMemo(() => !leftPinned())
+  const showHeaderSessionTitle = createMemo(() => !compactHeaderLayout() && showHeaderLeftSlot() && Boolean(activeSessionTitle()))
+  const headerToolbarHorizontalInset = createMemo(() => (isPhoneLayout() ? 16 : 24))
+  const headerLeftSlotWidth = createMemo(() => Math.max(0, sessionSidebarWidth() - headerToolbarHorizontalInset()))
+  const headerLeftSlotStyle = createMemo(() =>
+    leftDrawerState() === "floating-open" || showHeaderSessionTitle() ? { width: `${headerLeftSlotWidth()}px` } : undefined,
+  )
+
+  const renderActiveSessionHeaderTitle = () => (
+    <Show when={showHeaderSessionTitle()}>
+      <div
+        class="session-header-active-title"
+        dir="auto"
+        title={activeSessionTitle() ?? undefined}
+      >
+        <span class="session-header-active-title-text">{activeSessionTitle()}</span>
+      </div>
+    </Show>
+  )
+
+  const renderHeaderLeftSlot = () => (
+    <Show when={showHeaderLeftSlot()}>
+      <div class="session-header-left-slot" style={headerLeftSlotStyle()}>
+        <Show when={leftDrawerState() === "floating-closed"}>
+          <IconButton
+            ref={setLeftToggleButtonEl}
+            color="inherit"
+            onClick={handleLeftAppBarButtonClick}
+            aria-label={leftAppBarButtonLabel()}
+            size="small"
+            aria-expanded={leftDrawerState() !== "floating-closed"}
+          >
+            {leftAppBarButtonIcon()}
+          </IconButton>
+        </Show>
+        {renderActiveSessionHeaderTitle()}
+      </div>
+    </Show>
+  )
 
   const isLaunching = createMemo(() => props.instance.status === "starting")
 
@@ -933,94 +994,76 @@ const InstanceShell2: Component<InstanceShellProps> = (props) => {
                 fallback={
                   <div class="flex flex-col w-full gap-1.5">
                     <div class="flex flex-wrap items-center justify-between gap-2 w-full">
-                    <Show when={leftDrawerState() === "floating-closed"}>
-                      <IconButton
-                        ref={setLeftToggleButtonEl}
-                        color="inherit"
-                        onClick={handleLeftAppBarButtonClick}
-                        aria-label={leftAppBarButtonLabel()}
-                        size="small"
-                        aria-expanded={leftDrawerState() !== "floating-closed"}
-                      >
-                       {leftAppBarButtonIcon()}
-                      </IconButton>
-                    </Show>
+                      {renderHeaderLeftSlot()}
 
-                    <div class="flex-1 flex items-center justify-center min-w-0">
-                      {renderSessionHeaderIndicators()}
-                    </div>
+                      <div class="flex-1 flex items-center justify-center min-w-0">
+                        {renderSessionHeaderIndicators()}
+                      </div>
 
-                    <div class="flex flex-wrap items-center justify-center gap-1">
-                      <Show when={!showingInfoView()}>
+                      <div class="flex flex-wrap items-center justify-center gap-1">
+                        <Show when={!showingInfoView()}>
+                          <IconButton
+                            color="inherit"
+                            onClick={handleChatSearchClick}
+                            aria-label={t("instanceShell.chatSearch.openAriaLabel")}
+                            title={t("instanceShell.chatSearch.openAriaLabel")}
+                            size="small"
+                          >
+                            <Search class="w-5 h-5" aria-hidden="true" />
+                          </IconButton>
+                        </Show>
+                        <button
+                          type="button"
+                          class="connection-status-button command-palette-button"
+                          onClick={handleCommandPaletteClick}
+                          aria-label={t("instanceShell.commandPalette.openAriaLabel")}
+                          style={{ flex: "0 0 auto", width: "auto" }}
+                        >
+                          {t("instanceShell.commandPalette.button")}
+                        </button>
+                        <span class="connection-status-shortcut-hint kbd-hint">
+                          <Kbd shortcut="cmd+shift+p" />
+                        </span>
+                      </div>
+
+                      <div class="flex-1 flex items-center justify-center min-w-0">
+                        <span
+                          class={`status-indicator ${connectionStatusClass()}`}
+                          aria-label={t("instanceShell.connection.ariaLabel", { status: connectionStatusLabel() })}
+                        >
+                          <span class="status-dot" />
+                        </span>
+                      </div>
+
+                      <Show when={!isPhoneLayout()}>
+                        {renderPreviewToggleButton()}
+                      </Show>
+
+                      <Show when={isPhoneLayout() && !props.mobileFullscreenMode}>
                         <IconButton
                           color="inherit"
-                          onClick={handleChatSearchClick}
-                          aria-label={t("instanceShell.chatSearch.openAriaLabel")}
-                          title={t("instanceShell.chatSearch.openAriaLabel")}
+                          onClick={props.onEnterMobileFullscreen}
+                          aria-label={t("instanceShell.fullscreen.enter")}
+                          title={t("instanceShell.fullscreen.enter")}
                           size="small"
                         >
-                          <Search class="w-5 h-5" aria-hidden="true" />
+                          <Maximize2 class="w-5 h-5" aria-hidden="true" />
                         </IconButton>
+                        {renderPreviewToggleButton()}
+                      </Show>
+
+                      <Show when={rightDrawerState() === "floating-closed"}>
                         <IconButton
+                          ref={setRightToggleButtonEl}
                           color="inherit"
-                          onClick={handlePreviewButtonClick}
-                          aria-label={previewToggleLabel()}
-                          title={previewToggleLabel()}
+                          onClick={handleRightAppBarButtonClick}
+                          aria-label={rightAppBarButtonLabel()}
                           size="small"
+                          aria-expanded={rightDrawerState() !== "floating-closed"}
                         >
-                          {(() => {
-                            const Icon = PreviewToggleIcon()
-                            return <Icon class="w-5 h-5" aria-hidden="true" />
-                          })()}
+                          {rightAppBarButtonIcon()}
                         </IconButton>
                       </Show>
-                      <button
-                        type="button"
-                        class="connection-status-button command-palette-button"
-                        onClick={handleCommandPaletteClick}
-                        aria-label={t("instanceShell.commandPalette.openAriaLabel")}
-                        style={{ flex: "0 0 auto", width: "auto" }}
-                      >
-                        {t("instanceShell.commandPalette.button")}
-                      </button>
-                      <span class="connection-status-shortcut-hint kbd-hint">
-                        <Kbd shortcut="cmd+shift+p" />
-                     </span>
-                     </div>
-
-                    <div class="flex-1 flex items-center justify-center min-w-0">
-                      <span
-                        class={`status-indicator ${connectionStatusClass()}`}
-                        aria-label={t("instanceShell.connection.ariaLabel", { status: connectionStatusLabel() })}
-                      >
-                        <span class="status-dot" />
-                      </span>
-                    </div>
-
-                    <Show when={isPhoneLayout() && !props.mobileFullscreenMode}>
-                      <IconButton
-                        color="inherit"
-                        onClick={props.onEnterMobileFullscreen}
-                        aria-label={t("instanceShell.fullscreen.enter")}
-                        title={t("instanceShell.fullscreen.enter")}
-                        size="small"
-                      >
-                        <Maximize2 class="w-5 h-5" aria-hidden="true" />
-                      </IconButton>
-                    </Show>
-
-                    <Show when={rightDrawerState() === "floating-closed"}>
-                      <IconButton
-                        ref={setRightToggleButtonEl}
-                        color="inherit"
-                        onClick={handleRightAppBarButtonClick}
-                        aria-label={rightAppBarButtonLabel()}
-                        size="small"
-                        aria-expanded={rightDrawerState() !== "floating-closed"}
-                      >
-                        {rightAppBarButtonIcon()}
-                      </IconButton>
-                    </Show>
                     </div>
 
                     <div class="flex flex-wrap items-center justify-center gap-2 pb-1">
@@ -1038,18 +1081,7 @@ const InstanceShell2: Component<InstanceShellProps> = (props) => {
               }
             >
               <div class="session-toolbar-left flex-1 flex items-center gap-3 min-w-0">
-                <Show when={leftDrawerState() === "floating-closed"}>
-                  <IconButton
-                    ref={setLeftToggleButtonEl}
-                    color="inherit"
-                    onClick={handleLeftAppBarButtonClick}
-                    aria-label={leftAppBarButtonLabel()}
-                    size="small"
-                    aria-expanded={leftDrawerState() !== "floating-closed"}
-                  >
-                    {leftAppBarButtonIcon()}
-                  </IconButton>
-                </Show>
+                {renderHeaderLeftSlot()}
 
                 <Show when={!showingInfoView()}>
                   <ContextMeter
@@ -1095,18 +1127,7 @@ const InstanceShell2: Component<InstanceShellProps> = (props) => {
                       >
                         <Search class="w-5 h-5" aria-hidden="true" />
                       </IconButton>
-                      <IconButton
-                        color="inherit"
-                        onClick={handlePreviewButtonClick}
-                        aria-label={previewToggleLabel()}
-                        title={previewToggleLabel()}
-                        size="small"
-                      >
-                        {(() => {
-                          const Icon = PreviewToggleIcon()
-                          return <Icon class="w-5 h-5" aria-hidden="true" />
-                        })()}
-                      </IconButton>
+                      {renderPreviewToggleButton()}
                     </Show>
                     <Show when={connectionStatus() === "connected"}>
                       <span class="status-indicator connected">

packages/ui/src/styles/panels/session-layout.css

@@ -105,6 +105,32 @@
   color: var(--text-primary);
 }
 
+.session-header-left-slot {
+  @apply flex items-center gap-2 min-w-0;
+  flex: 0 0 auto;
+}
+
+.session-header-active-title {
+  display: flex;
+  align-items: center;
+  flex: 1 1 auto;
+  min-width: 0;
+  align-self: stretch;
+  padding-inline: 0.75rem;
+  border-inline: 1px solid color-mix(in oklab, var(--border-base) 72%, transparent);
+  color: var(--text-secondary);
+}
+
+.session-header-active-title-text {
+  display: -webkit-box;
+  -webkit-line-clamp: 2;
+  -webkit-box-orient: vertical;
+  overflow: hidden;
+  font-size: 0.8125rem;
+  font-weight: 500;
+  line-height: 1.15;
+}
+
 .session-sidebar-shortcuts {
   @apply flex flex-col gap-1;
 }