feat: shared PaneHeaderActions + chat-resolve WorkspaceState fix (v2.7.7)

In-flight workspace UX work.

- Extract a shared PaneHeaderActions cluster (+/Split/Reopen/History/Close)
  used by ChatTabBar + the Workspace coder/terminal pane headers, replacing the
  divergent per-header copies; SessionLandingPage history + useWorkspacePanes
  tweaks.
- Fix coder-side correctness bug: resolveChatId read sessions.workspace_panes as
  a bare WorkspacePane[] but v2.6.5 widened it to a WorkspaceState envelope, so
  it mis-read panes and clobbered tabNumbers/nextTabNumber/closedPaneStack on
  every pane-chat write. New normalizeWorkspaceState handles either shape and
  preserves the envelope (+ regression test).
- CLAUDE.md doc-sync (coder vitest suite, deploy-by-surface, dual-remote push,
  in-flight-web-WIP staging, release-branch naming).

Web tsc + coder build + coder tests green. Builds on v2.7.6.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

apps/coder/src/routes/__tests__/chat-resolve.test.ts

@@ -0,0 +1,110 @@
+import { describe, it, expect } from 'vitest';
+import { resolveChatId } from '../chat-resolve.js';
+import type { Sql } from '../../db.js';
+
+// Mock the porsager/postgres surface that chat-resolve.ts uses: a tagged-template
+// `tx` (dispatched by query substring), `tx.json`, and `sql.begin(fn)` which just
+// runs fn(tx). Captures the value written back to workspace_panes so we can assert
+// the WorkspaceState envelope survives the UPDATE.
+interface MockState {
+  stored: unknown; // initial sessions.workspace_panes value
+  existingChatOpen: boolean; // whether `SELECT id FROM chats ...` finds the active chat
+  newChatId: string;
+  written?: unknown; // captured tx.json(...) payload from `UPDATE sessions`
+  inserted: boolean; // whether INSERT INTO chats ran
+}
+
+interface MockTx {
+  (strings: TemplateStringsArray): Promise<unknown>;
+  json: (v: unknown) => unknown;
+}
+
+function mockSql(state: MockState): Sql {
+  const tx = ((strings: TemplateStringsArray) => {
+    const q = strings.join('');
+    if (q.includes('SELECT workspace_panes FROM sessions')) {
+      return Promise.resolve([{ workspace_panes: state.stored }]);
+    }
+    if (q.includes('FROM chats')) {
+      return Promise.resolve(state.existingChatOpen ? [{ id: 'placeholder' }] : []);
+    }
+    if (q.includes('INSERT INTO chats')) {
+      state.inserted = true;
+      return Promise.resolve([{ id: state.newChatId }]);
+    }
+    if (q.includes('UPDATE sessions')) {
+      return Promise.resolve([]);
+    }
+    return Promise.resolve([]);
+  }) as unknown as MockTx;
+  tx.json = (v: unknown) => {
+    state.written = v;
+    return v;
+  };
+  const sql = {
+    begin: (fn: (t: Sql) => Promise<unknown>) => fn(tx as unknown as Sql),
+  };
+  return sql as unknown as Sql;
+}
+
+const ENVELOPE = () => ({
+  panes: [{ id: 'pane-1', kind: 'coder', chatIds: [] as string[], activeChatIdx: 0 }],
+  tabNumbers: { 'chat-x': 3 },
+  nextTabNumber: 7,
+  closedPaneStack: [{ kind: 'coder', chatIds: ['old'], activeChatIdx: 0 }],
+});
+
+describe('resolveChatId — v2.6.5 WorkspaceState envelope', () => {
+  it('reads panes from the envelope without crashing (regression: panes.findIndex is not a function)', async () => {
+    const state: MockState = {
+      stored: ENVELOPE(),
+      existingChatOpen: false,
+      newChatId: 'new-chat-1',
+      inserted: false,
+    };
+    const chatId = await resolveChatId(mockSql(state), 'session-1', 'pane-1');
+    expect(chatId).toBe('new-chat-1');
+    expect(state.inserted).toBe(true);
+  });
+
+  it('preserves the envelope (tabNumbers/nextTabNumber/closedPaneStack) on write-back', async () => {
+    const state: MockState = {
+      stored: ENVELOPE(),
+      existingChatOpen: false,
+      newChatId: 'new-chat-1',
+      inserted: false,
+    };
+    await resolveChatId(mockSql(state), 'session-1', 'pane-1');
+    const w = state.written as Record<string, unknown>;
+    expect(Array.isArray(w.panes)).toBe(true); // envelope, not a bare array
+    expect(w.tabNumbers).toEqual({ 'chat-x': 3 });
+    expect(w.nextTabNumber).toBe(7);
+    expect(w.closedPaneStack).toEqual([{ kind: 'coder', chatIds: ['old'], activeChatIdx: 0 }]);
+  });
+
+  it('returns the existing open chat when the pane already has one', async () => {
+    const env = ENVELOPE();
+    env.panes[0]!.chatIds = ['existing-1'];
+    const state: MockState = {
+      stored: env,
+      existingChatOpen: true,
+      newChatId: 'should-not-be-used',
+      inserted: false,
+    };
+    const chatId = await resolveChatId(mockSql(state), 'session-1', 'pane-1');
+    expect(chatId).toBe('existing-1');
+    expect(state.inserted).toBe(false);
+  });
+
+  it('still accepts a legacy bare WorkspacePane[] array', async () => {
+    const state: MockState = {
+      stored: [{ id: 'pane-1', kind: 'coder', chatId: 'legacy-1', chatIds: ['legacy-1'], activeChatIdx: 0 }],
+      existingChatOpen: true,
+      newChatId: 'should-not-be-used',
+      inserted: false,
+    };
+    const chatId = await resolveChatId(mockSql(state), 'session-1', 'pane-1');
+    expect(chatId).toBe('legacy-1');
+    expect(state.inserted).toBe(false);
+  });
+});