feat(desktop): Linux AppImage releases and desktop feature parity (#2398)

* feat(electron): add Linux AppImage releases

* ci: cache Linux OpenCode CLI artifacts

* fix(ci): await Linux release inventory check

* fix(electron): add frameless window controls on Linux desktop

Linux AppImages were created without native WM decorations and without
in-app controls, leaving users unable to close the window with a mouse.

Treat Linux like Windows: frameless BrowserWindow plus the existing
WindowsWindowControls header buttons and app-menu entry. macOS keeps
hidden title bar with traffic lights unchanged.

Shared usesFramelessElectronChrome() helper drives main window, mini
chat, header insets, and titlebar controls.

Co-authored-by: Serhii Dziupin <makeittech@users.noreply.github.com>

* Linux desktop feature parity: Open in, background start, tray, multi-window (#2392)

* feat(electron): Linux parity for Open in, background start, and tray

Enable Linux desktop feature parity with macOS/Windows: open projects in
the default file manager and discovered apps, XDG autostart with
--background launches, system tray (including minimize-to-tray), and
tray sync from the renderer.

Co-authored-by: Serhii Dziupin <makeittech@users.noreply.github.com>

* fix(electron): allow packaged UI protocol navigations on Linux

Prevent openchamber-ui:// navigations from being handed to
shell.openExternal, which fails on Linux and blocked desktop UI flows.

Co-authored-by: Serhii Dziupin <makeittech@users.noreply.github.com>

* fix(ui): surface Linux tray settings in settings search

Include isLinux in settings search runtime context so minimize-to-tray
is discoverable on Linux desktop, matching Windows search behavior.

Co-authored-by: Serhii Dziupin <makeittech@users.noreply.github.com>

* fix(electron): stop Linux AppImage Waiting-for-OpenCode flicker

Sync updated boot-outcome init scripts to all BrowserWindows after
desktop_hosts_set, and prefer state.initScript on dom-ready so chooser
reloads inject local/ok instead of a stale not-configured outcome.

Co-authored-by: Serhii Dziupin <makeittech@users.noreply.github.com>

---------

Co-authored-by: Cursor Agent <cursoragent@cursor.com>
Co-authored-by: Serhii Dziupin <makeittech@users.noreply.github.com>

* fix(desktop): restore Linux AppImage updater feed and error UX (#2396)

Treat missing latest-linux*.yml (404) as no update available instead of a
hard failure, and stop swallowing updater capability/download errors in the
desktop bridge so About/sidebar can show actionable messages.

Co-authored-by: Cursor Agent <cursoragent@cursor.com>
Co-authored-by: Serhii Dziupin <makeittech@users.noreply.github.com>

* docs: credit Linux AppImage contributors in changelog

Co-authored-by: Serhii Dziupin <makeittech@users.noreply.github.com>

---------

Co-authored-by: jibanez-staticduo <staticduo@gmail.com>
Co-authored-by: Serhii Dziupin <makeittech@users.noreply.github.com>

packages/ui/src/hooks/useTraySync.ts

@@ -104,7 +104,7 @@ type DesktopBridgeGlobal = {
 const isTrayPlatform = (): boolean => {
   if (typeof window === 'undefined') return false;
   const platform = (window as unknown as { __OPENCHAMBER_PLATFORM__?: string }).__OPENCHAMBER_PLATFORM__;
-  return platform === 'darwin' || platform === 'win32';
+  return platform === 'darwin' || platform === 'win32' || platform === 'linux';
 };
 
 const isTrayEnabled = (): boolean =>