feat(desktop): Linux AppImage polish — window controls, updater UX, docs (#2144)

* 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>

* feat(desktop): add configurable window controls position by OS

Add desktopWindowControlsPosition setting (auto/left/right) with OS-aware
defaults: Linux left, Windows right. Wire frameless chrome controls in
Header, TitlebarLeftControls, and MiniChatLayout, plus a Sessions settings
control for Windows and Linux desktop shells.

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

* fix(desktop): address Linux AppImage release review findings

Propagate updater capability errors to the UI, treat missing
latest-linux.yml feeds as no-update, stop installed-apps IPC spam on
Linux, document FUSE/AppImage limits, add CHANGELOG entry, migrate
remaining btriapitsyn URLs, and run Electron Linux unit tests on PRs.

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/lib/i18n/messages/ja.settings.ts

@@ -893,6 +893,12 @@ export const settingsDict = {
   'settings.openchamber.sessionRetention.toast.failedArchiveCount': '{count} 個の Session のアーカイブに失敗しました',
   'settings.openchamber.sessionRetention.toast.failedDeleteCount': '{count} 個の Session の削除に失敗しました',
   'settings.openchamber.desktopNetwork.title': 'Desktop ネットワークアクセス',
+  'settings.openchamber.desktopNetwork.field.windowControlsPosition': 'ウィンドウコントロールの位置',
+  'settings.openchamber.desktopNetwork.field.windowControlsPositionDescription': '最小化・最大化・閉じるボタンの表示位置を選びます。自動は OS に合わせます。',
+  'settings.openchamber.desktopNetwork.field.windowControlsPositionAria': 'ウィンドウコントロールの位置',
+  'settings.openchamber.desktopNetwork.option.windowControlsAuto': '自動',
+  'settings.openchamber.desktopNetwork.option.windowControlsLeft': '左',
+  'settings.openchamber.desktopNetwork.option.windowControlsRight': '右',
   'settings.openchamber.desktopNetwork.field.launchAtLoginAria': 'ログイン時に OpenChamber を起動',
   'settings.openchamber.desktopNetwork.field.launchAtLogin': 'ログイン時に OpenChamber を起動',
   'settings.openchamber.desktopNetwork.field.launchAtLoginDescription': 'ウィンドウを開かずにバックグラウンドでアプリを起動します。デスクトップのステータスアイコンから開けます。',