refactor(desktop): make Tauri thin shell running web sidecar (#273)

## What / Why
This PR finishes the desktop refactor: the Tauri app is now a thin shell that launches the web server as a sidecar and loads the UI from `http://127.0.0.1:<port>`. All real backend logic lives in `packages/web/server/index.js`; desktop Rust keeps only native integrations (menu/dialog/notifications/updater/deep-link + window chrome).
This unblocks:
- consistent behavior across web/desktop/vscode (single backend)
- simpler desktop maintenance (no duplicated Rust backend)
- host switching between Local + remote instances in desktop
- reliable cold-start behavior on slow machines (VSCode + desktop)
## Key changes
- Desktop sidecar runtime
  - build pipeline to bundle web dist + `openchamber-server` sidecar (`packages/desktop/scripts/build-sidecar.mjs`)
  - robust local port selection (prefer saved/default, fallback to random; persisted in `~/.config/openchamber/settings.json`)
  - improved PATH handling so the sidecar can locate `opencode` CLI (incl `~/.opencode/bin`, overrides, common bins)
  - disable native right-click context menu in production builds (dev keeps it)
- Desktop instance switcher (Tauri-only)
  - header button + modal to add/edit/delete remote hosts, set default, probe status/ping, switch back to Local escape hatch
  - auth gate includes host switcher so you can recover when a remote host is broken/auth-required
  - host list stored desktop-locally (not tied to the currently selected remote server)
- Notifications
  - decision logic moved server-side; desktop notifications emitted via sidecar stdout and shown natively by Tauri
  - prevent double-notifications on desktop Local origin (UI ignores SSE notification when native path is active)
  - restore macOS notification sound
- Updates
  - Tauri updater used only when viewing Local instance in desktop shell (avoid “remote web update” triggering desktop restart)
- Settings persistence & UX polish
  - persist model favorites/recents via `/api/config/settings` (works for web + desktop; not origin-dependent)
  - persist per-project sidebar collapse state in `projects[].sidebarCollapsed` via `/api/config/settings` (with debounce on toggles)
  - macOS header sizing/traffic-lights offsets fixed (marketing macOS major injected from desktop; MultiRun header aligned)
  - VSCode cold-start: keep retrying provider/agent loads after connection to avoid empty UI on slow machines
  - misc lint/type fixes + bun.lock sync
- Desktop bootstrap / resiliency
  - show onboarding screen when OpenCode CLI is missing (desktop Local origin), with retry hook to restart OpenCode after install
## Testing notes
- Desktop (macOS): switch Local <-> remote, set default host, verify auth gate recovery, native notifications (with sound), updater gated to Local
- Web: favorites/recents + per-project collapsed state persist across reload/restart
- VSCode: slow startup no longer results in missing providers/agents/models

packages/ui/src/components/chat/ChatInput.tsx

@@ -232,6 +232,9 @@ export const ChatInput: React.FC<ChatInputProps> = ({ onOpenSettings, scrollToBo
 
     const canAbort = working.isWorking;
 
+    // Keep a ref to handleSubmit so callbacks don't depend on it.
+    const handleSubmitRef = React.useRef<(e?: React.FormEvent) => Promise<void>>(async () => {});
+
     // Add message to queue instead of sending
     const handleQueueMessage = React.useCallback(() => {
         if (!hasContent || !currentSessionId) return;
@@ -448,23 +451,21 @@ export const ChatInput: React.FC<ChatInputProps> = ({ onOpenSettings, scrollToBo
         }
     };
 
+    handleSubmitRef.current = handleSubmit;
+
     // Primary action for send button - respects queue mode setting
     const handlePrimaryAction = React.useCallback(() => {
         const canQueue = hasContent && currentSessionId && sessionPhase !== 'idle';
         if (queueModeEnabled && canQueue) {
             handleQueueMessage();
         } else {
-            void handleSubmit();
+            void handleSubmitRef.current();
         }
-    }, [hasContent, currentSessionId, sessionPhase, queueModeEnabled, handleQueueMessage, handleSubmit]);
-
-    // Keep a ref to handleSubmit for auto-send effect
-    const handleSubmitRef = React.useRef(handleSubmit);
-    handleSubmitRef.current = handleSubmit;
+    }, [hasContent, currentSessionId, sessionPhase, queueModeEnabled, handleQueueMessage]);
 
     // Auto-send queued messages when session becomes idle (but not after abort)
     React.useEffect(() => {
-        const wasWorking = prevSessionPhaseRef.current === 'busy' || prevSessionPhaseRef.current === 'cooldown';
+        const wasWorking = prevSessionPhaseRef.current === 'busy' || prevSessionPhaseRef.current === 'retry';
         const isNowIdle = sessionPhase === 'idle';
 
         // Check if session was recently aborted (within last 2 seconds)
@@ -1483,8 +1484,6 @@ export const ChatInput: React.FC<ChatInputProps> = ({ onOpenSettings, scrollToBo
                     isWaitingForPermission={working.isWaitingForPermission}
                     wasAborted={working.wasAborted}
                     abortActive={working.abortActive}
-                    completionId={working.lastCompletionId}
-                    isComplete={working.isComplete}
                     showAbortStatus={showAbortStatus}
                 />
             </div>