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/web/src/hooks/useWorkspacePanes.ts

@@ -640,13 +640,23 @@ export function useWorkspacePanes(sessionId: string): UseWorkspacePanesResult {
   const showLandingPage = useCallback((paneIdx: number) => {
     setPanes((prev) => {
       const pane = prev[paneIdx];
-      // Coder/terminal panes are not chat hosts — history button is chat-only.
-      if (!pane || pane.kind === 'coder' || pane.kind === 'terminal') return prev;
+      if (!pane) return prev;
       const next = [...prev];
-      next[paneIdx] = { ...pane, kind: 'empty', chatId: undefined };
+      if (pane.kind === 'coder' || pane.kind === 'terminal') {
+        // Scoped panes don't host chat tabs. Leaving one for the session
+        // history closes it: drop the pane→chat binding, and for terminals
+        // kill the tmux session (terminals are ephemeral — closing = killing,
+        // mirroring removePane).
+        if (pane.kind === 'terminal') {
+          api.terminals.kill(sessionId, pane.id).catch(() => { /* non-fatal */ });
+        }
+        next[paneIdx] = { ...pane, kind: 'empty', chatId: undefined, chatIds: [], activeChatIdx: -1 };
+      } else {
+        next[paneIdx] = { ...pane, kind: 'empty', chatId: undefined };
+      }
       return next;
     });
-  }, []);
+  }, [sessionId]);
 
   const addSplitPane = useCallback((kind: 'chat' | 'terminal' | 'coder'): string | null => {
     // Generate the id outside the updater so we can return it deterministically.