Keep right-canvas surface rail docked

Route right-canvas rail clicks through the explicit canvas opener so Browser, Editor, Files, and Desktop open in the canvas even after a modal session. Preserve modal-header surface switches as floating modal entry points, and document/test the entry-point split.

tests/test_browser_agent_regressions.py

@@ -803,7 +803,7 @@ def test_browser_entry_points_prefer_canvas_and_modal_dock_handoff():
         assert "Alpine.store" not in js
 
 
-def test_browser_and_desktop_surface_buttons_remember_latest_window_mode():
+def test_surface_buttons_keep_modal_and_canvas_entry_points_separate():
     canvas_store = (PROJECT_ROOT / "webui" / "components" / "canvas" / "right-canvas-store.js").read_text(
         encoding="utf-8"
     )
@@ -852,8 +852,8 @@ def test_browser_and_desktop_surface_buttons_remember_latest_window_mode():
     assert "this.mountedSurfaces = {}" not in open_modal_block
     assert "failed to close before modal open" not in open_modal_block
 
-    assert '@click="$store.rightCanvas.openLatest(surface.id)"' in canvas_html
-    assert '@click="$store.rightCanvas.open(surface.id)"' in canvas_html
+    assert '@click="$store.rightCanvas.openLatest(surface.id)"' not in canvas_html
+    assert canvas_html.count('@click="$store.rightCanvas.open(surface.id)"') == 2
 
     assert "recordMode(metadata.surfaceId, SURFACE_MODE_FLOATING)" in surfaces_js
     assert "configureModalSurfaceSwitcher" in surfaces_js

webui/components/canvas/AGENTS.md

@@ -14,6 +14,7 @@
 
 - Keep registered surfaces compatible with WebUI extension hooks.
 - Preserve responsive layout and avoid overlapping the chat/sidebar shells.
+- Right-canvas rail and tab buttons are explicit canvas entry points; they must open surfaces in the canvas even when the same surface was last used as a floating modal.
 
 ## Work Guidance
 

webui/components/canvas/right-canvas.html

@@ -46,7 +46,7 @@
               :class="{ 'is-active': $store.rightCanvas.isSurfaceActive(surface.id) && $store.rightCanvas.isOpen }"
               :title="surface.title"
               :aria-label="surface.title"
-              @click="$store.rightCanvas.openLatest(surface.id)"
+              @click="$store.rightCanvas.open(surface.id)"
             >
               <template x-if="surface.image">
                 <img class="right-canvas-surface-image" :src="surface.image" alt="" aria-hidden="true">