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/lib/device.ts

@@ -1,4 +1,5 @@
 import React from 'react';
+import { isTauriShell } from '@/lib/desktop';
 
 export type DeviceType = 'desktop' | 'mobile' | 'tablet';
 
@@ -28,7 +29,7 @@ export const BREAKPOINTS = {
 } as const;
 
 const setRootDeviceAttributes = (
-  isDesktopRuntime: boolean,
+  isTauriShellRuntime: boolean,
   deviceType: DeviceType,
   hasTouchInput: boolean,
 ) => {
@@ -49,7 +50,7 @@ const setRootDeviceAttributes = (
         : 'device-desktop'
   );
 
-  if (isDesktopRuntime) {
+  if (isTauriShellRuntime) {
     root.classList.add('desktop-runtime');
     root.style.setProperty('--is-mobile', '0');
     root.style.setProperty('--device-type', 'desktop');
@@ -81,7 +82,7 @@ export function getDeviceInfo(): DeviceInfo {
   const noHover = hoverQuery?.matches ?? false;
   const maxTouchPoints = typeof navigator !== 'undefined' ? navigator.maxTouchPoints ?? 0 : 0;
 
-  const isDesktopRuntime = typeof window !== 'undefined' && typeof window.opencodeDesktop !== 'undefined';
+  const isTauriShellRuntime = isTauriShell();
 
   const hasTouchInput = prefersCoarsePointer || noHover || maxTouchPoints > 0;
 
@@ -93,7 +94,7 @@ export function getDeviceInfo(): DeviceInfo {
   let isDesktop = !hasTouchInput || width > BREAKPOINTS.lg;
   let deviceType: DeviceType = 'desktop';
 
-  if (isDesktopRuntime) {
+  if (isTauriShellRuntime) {
     isMobile = false;
     isTablet = false;
     isDesktop = true;
@@ -107,7 +108,7 @@ export function getDeviceInfo(): DeviceInfo {
     deviceType = 'desktop';
   }
 
-  setRootDeviceAttributes(isDesktopRuntime, deviceType, hasTouchInput);
+  setRootDeviceAttributes(isTauriShellRuntime, deviceType, hasTouchInput);
 
   let breakpoint: keyof typeof BREAKPOINTS = 'xs';
   for (const [key, value] of Object.entries(BREAKPOINTS)) {
@@ -130,7 +131,7 @@ export function getDeviceInfo(): DeviceInfo {
 export function isMobileDeviceViaCSS(): boolean {
   if (typeof window === 'undefined') return false;
 
-  if (typeof window.opencodeDesktop !== 'undefined') {
+  if (typeof window !== 'undefined' && isTauriShell()) {
     return false;
   }
 
@@ -205,7 +206,7 @@ export function useDeviceInfo(): DeviceInfo {
 
   React.useEffect(() => {
     if (typeof window === 'undefined') return;
-    const isDesktopRuntime = typeof window.opencodeDesktop !== 'undefined';
+    const isTauriShellRuntime = isTauriShell();
     const supportsMatchMedia = typeof window.matchMedia === 'function';
     const pointerQuery = supportsMatchMedia ? window.matchMedia('(pointer: coarse)') : null;
     const hoverQuery = supportsMatchMedia ? window.matchMedia('(hover: none)') : null;
@@ -213,7 +214,7 @@ export function useDeviceInfo(): DeviceInfo {
     const noHover = hoverQuery?.matches ?? false;
     const maxTouchPoints = typeof navigator !== 'undefined' ? navigator.maxTouchPoints ?? 0 : 0;
     const hasTouchInput = prefersCoarsePointer || noHover || maxTouchPoints > 0;
-    setRootDeviceAttributes(isDesktopRuntime, deviceInfo.deviceType, hasTouchInput);
+    setRootDeviceAttributes(isTauriShellRuntime, deviceInfo.deviceType, hasTouchInput);
   }, [deviceInfo.deviceType, deviceInfo.hasTouchInput]);
 
   return deviceInfo;