fix(web): adapt steer/session-url tests and stub daemon to snapshot sync

The snapshot-based session resync (51743345) replaced listMessages with
GET /sessions/{id}/snapshot as the initial sync path. Update the two
test suites that predate it (mock getSessionSnapshot + seedSnapshot,
assert on the snapshot call) and teach the dev stub daemon the
/snapshot route so pnpm dev:stub keeps working.

apps/kimi-web/dev/stub-daemon.mjs

@@ -1072,6 +1072,21 @@ const server = http.createServer((req, res) => {
       }
     }
 
+    // ---- snapshot (v2 initial sync: GET /sessions/{id}/snapshot) ----
+    if (seg[0] === 'sessions' && seg[2] === 'snapshot' && seg.length === 3 && method === 'GET') {
+      const session = sessions.find((s) => s.id === sid);
+      if (!session) return res.end(fail(40401, `session ${sid} does not exist`));
+      return res.end(ok({
+        as_of_seq: seqBySession[sid] || 0,
+        epoch: 'ep_stub',
+        session,
+        messages: { items: messages[sid] || [], has_more: false },
+        in_flight_turn: null,
+        pending_approvals: [],
+        pending_questions: [],
+      }));
+    }
+
     // ---- messages ----
     if (seg[0] === 'sessions' && seg[2] === 'messages' && seg.length === 3 && method === 'GET') {
       const sp = new URLSearchParams(url.split('?')[1] || '');

apps/kimi-web/test/session-url.test.ts

@@ -57,6 +57,7 @@ async function setup(opts: {
     subscribe: vi.fn(),
     unsubscribe: vi.fn(),
     bindNextPromptId: vi.fn(),
+    seedSnapshot: vi.fn(),
     abort: vi.fn(),
     close: vi.fn(),
   };
@@ -74,11 +75,21 @@ async function setup(opts: {
       return found;
     }),
     deleteSession: vi.fn(async () => ({ deleted: true })),
-    listMessages: vi.fn(async (id: string) => {
+    getSessionSnapshot: vi.fn(async (id: string) => {
       if (messageMissingSessions.has(id)) {
         throw { name: 'DaemonApiError', code: 40401, message: `session ${id} does not exist` };
       }
-      return { items: [], hasMore: false };
+      const found = extras.find((s) => s.id === id) ?? listed.find((s) => s.id === id) ?? session(id);
+      return {
+        asOfSeq: 0,
+        epoch: 'ep_test',
+        session: found,
+        messages: [],
+        hasMoreMessages: false,
+        inFlightTurn: null,
+        pendingApprovals: [],
+        pendingQuestions: [],
+      };
     }),
     listTasks: vi.fn(async () => []),
     getGitStatus: vi.fn(async () => ({ branch: 'main', ahead: 0, behind: 0, entries: {} })),
@@ -196,7 +207,7 @@ describe('session ↔ URL binding', () => {
     expect(window.location.pathname).toBe('/sessions/sess_1');
   });
 
-  it('load() repairs a deep link when the listed session vanishes before messages load', async () => {
+  it('load() repairs a deep link when the listed session vanishes before its snapshot loads', async () => {
     const { api, client } = await setup({
       sessions: [session('sess_gone'), session('sess_1')],
       messageMissingSessions: ['sess_gone'],
@@ -204,11 +215,11 @@ describe('session ↔ URL binding', () => {
     });
     await client.load();
 
-    expect(api.listMessages).toHaveBeenCalledWith('sess_gone', { pageSize: 100 });
+    expect(api.getSessionSnapshot).toHaveBeenCalledWith('sess_gone');
     expect(client.activeSessionId.value).toBe('sess_1');
     expect(client.sessions.value.map((s) => s.id)).toEqual(['sess_1']);
     expect(window.location.pathname).toBe('/sessions/sess_1');
-    expect(client.warnings.value.some((w) => w.includes('Failed to load messages'))).toBe(false);
+    expect(client.warnings.value.some((w) => w.includes('Failed to load session snapshot'))).toBe(false);
   });
 
   it('popstate selects the session from the URL without writing the URL again', async () => {

apps/kimi-web/test/steer.test.ts

@@ -43,6 +43,7 @@ async function setup(opts?: { submitStatuses?: ('running' | 'queued')[] }) {
     subscribe: vi.fn(),
     unsubscribe: vi.fn(),
     bindNextPromptId: vi.fn(),
+    seedSnapshot: vi.fn(),
     abort: vi.fn(),
     close: vi.fn(),
   };
@@ -51,7 +52,16 @@ async function setup(opts?: { submitStatuses?: ('running' | 'queued')[] }) {
   const created = session('sess_1');
   const api = {
     createSession: vi.fn(async () => created),
-    listMessages: vi.fn(async () => ({ items: [], hasMore: false })),
+    getSessionSnapshot: vi.fn(async () => ({
+      asOfSeq: 0,
+      epoch: 'ep_test',
+      session: created,
+      messages: [],
+      hasMoreMessages: false,
+      inFlightTurn: null,
+      pendingApprovals: [],
+      pendingQuestions: [],
+    })),
     submitPrompt: vi.fn(async () => {
       promptN += 1;
       return {