v1.12.1: rich status indicator + server-side workspace pane sync

Status indicator (StatusDot): drops the flat amber pulse for a richer set
of states — orbiting amber for streaming, spinning sky ring for tool_running,
static violet for waiting_for_input, plus the existing idle/error. Backend
chat_status frame widens from 'working|idle|error' to discriminate streaming
vs tool execution vs paused for user input.

Workspace pane sync: pane layout moves from per-device localStorage to
server-side sessions.workspace_panes jsonb. PATCH /api/sessions/:id/workspace
broadcasts session_workspace_updated on the user channel for cross-device live
sync. Echo dedup via JSON comparison so the round-trip frame doesn't loop.
Legacy localStorage seeds the server on first hydrate, then is deleted.
Deprecated session_panes table dropped.

Resilience: startup sweep marks any stale 'streaming' message older than
5 minutes as 'failed' so v1.12.0-style hung rows clear on container restart.
useWorkspacePanes gains validatePanes() to prune dead chatId references from
saved pane state when the chat list lands.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

apps/web/src/hooks/useSessionChats.ts

@@ -12,6 +12,7 @@ export interface UseSessionChatsOpts {
   // about pane indexing.
   openChatInActivePane: (chatId: string) => void;
   initializeFirstChatIfEmpty: (chatId: string) => void;
+  validatePanes: (validChatIds: Set<string>) => void;
 }
 
 export interface UseSessionChatsResult {
@@ -44,12 +45,15 @@ export function useSessionChats(
   openChatInActivePaneRef.current = opts.openChatInActivePane;
   const initializeFirstChatIfEmptyRef = useRef(opts.initializeFirstChatIfEmpty);
   initializeFirstChatIfEmptyRef.current = opts.initializeFirstChatIfEmpty;
+  const validatePanesRef = useRef(opts.validatePanes);
+  validatePanesRef.current = opts.validatePanes;
 
   useEffect(() => {
     let cancelled = false;
     api.chats.listForSession(sessionId).then((list) => {
       if (cancelled) return;
       setChats(list);
+      validatePanesRef.current(new Set(list.map((c) => c.id)));
       const openChat = list.find((c) => c.status === 'open');
       if (openChat) {
         initializeFirstChatIfEmptyRef.current(openChat.id);