v2.0.0: BooCoder frontend — chat pane + diff pane + session picker

Integrates BooCoder as a 'coder' workspace pane within the existing
BooChat SPA at code.indifferentketchup.com. Renamed the placeholder
'agent' pane kind to 'coder' across all types, menus, hooks, and
mobile switcher (Icon: Code instead of Bot).

CoderPane.tsx: split layout with chat area (messages via WS to
boocoder:9502, input bar posting to /api/coder/sessions/:id/messages)
and diff panel (pending changes with Approve/Reject per change plus
Approve All/Reject All). Reuses MarkdownRenderer for message content.

Proxy: Vite dev config adds /api/coder → boocoder:9502 (ordered above
/api per CLAUDE.md proxy-ordering rule). Production: Fastify route in
apps/server/src/index.ts proxies /api/coder/* to http://boocoder:3000
via fetch() pass-through. WS connects directly to :9502 (same
Tailscale network, no proxy needed for WebSocket upgrade).

WorkspacePaneKind mirror updated in both apps/web and apps/server
types. useWorkspacePanes gains coderPane() factory (replaces the old
agent toast stub). Workspace.tsx switch renders CoderPane for
pane.kind === 'coder'.

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

apps/web/src/hooks/useWorkspacePanes.ts

@@ -40,6 +40,13 @@ function terminalPane(id: string = generateId()): WorkspacePane {
   return { id, kind: 'terminal', chatIds: [], activeChatIdx: -1 };
 }
 
+// v2.0.0: coder pane — renders the BooCoder interface (chat + diff panel).
+// Like terminal panes, carries no chats — the CoderPane component manages
+// its own session/messages via the /api/coder proxy.
+function coderPane(id: string = generateId()): WorkspacePane {
+  return { id, kind: 'coder', chatIds: [], activeChatIdx: -1 };
+}
+
 // v1.9: settings pane factory. No chats, no state beyond identity — the
 // SettingsPane component renders Session/Project sections from the
 // surrounding session/project.
@@ -109,10 +116,10 @@ export interface UseWorkspacePanesResult {
   closeAllTabs: (paneIdx: number) => void;
   showLandingPage: (paneIdx: number) => void;
   // v1.10.3: returns the new pane's id (or null if the operation was a no-op:
-  // 'agent' kind is a toast stub, or max panes reached). Callers can use the
+  // max panes reached). Callers can use the
   // id to update mobile URL state so the URL-sync effect doesn't fight the
   // freshly-set activePaneIdx.
-  addSplitPane: (kind: 'chat' | 'terminal' | 'agent') => string | null;
+  addSplitPane: (kind: 'chat' | 'terminal' | 'coder') => string | null;
   // Open-on-first-click, close-on-second-click. Singleton — settings panes
   // don't count toward MAX_PANES. Closing the only remaining pane (edge case)
   // falls back to an empty pane to preserve the "always one pane" invariant.
@@ -388,11 +395,7 @@ export function useWorkspacePanes(sessionId: string): UseWorkspacePanesResult {
     });
   }, []);
 
-  const addSplitPane = useCallback((kind: 'chat' | 'terminal' | 'agent'): string | null => {
-    if (kind === 'agent') {
-      toast('Agent panes coming in BooCoder');
-      return null;
-    }
+  const addSplitPane = useCallback((kind: 'chat' | 'terminal' | 'coder'): string | null => {
     // Generate the id outside the updater so we can return it deterministically.
     // setPanes's updater can be invoked twice in strict mode; using a fixed id
     // ensures both invocations agree and the returned id matches what landed.
@@ -404,7 +407,10 @@ export function useWorkspacePanes(sessionId: string): UseWorkspacePanesResult {
         toast.error(`Maximum ${MAX_PANES} panes`);
         return prev;
       }
-      const newPane = kind === 'terminal' ? terminalPane(newPaneId) : emptyPane(newPaneId);
+      const newPane =
+        kind === 'terminal' ? terminalPane(newPaneId) :
+        kind === 'coder' ? coderPane(newPaneId) :
+        emptyPane(newPaneId);
       const next = [...prev, newPane];
       setActivePaneIdx(next.length - 1);
       success = true;