feat(gui): system-tray applet (M11) + GUI smoke tests — 0.19.0

QSystemTrayIcon applet (gui/tray.py, D13): menu with live CPU/GPU temp + memory
used/total, a status line, a Run Diagnostic submenu per detected game, plus Open
dashboard / Start-Stop recording / Snapshot-copy / Quit. Reuses the dashboard's
sample stream; drives existing MainWindow flows.

- MainWindow creates the tray when one is available; closing the window hides to
  tray (Quit exits); setQuitOnLastWindowClosed(False) so dialogs don't quit it.
- app: `--tray` starts hidden for autostart.
- tests/test_gui_smoke.py: construct MainWindow headless + exercise the tray, so
  a startup crash (like the 0.18.0 import bug) fails the build. Skips if no PySide6.
- docs: M10/M11 marked done in MODULES/ROADMAP.

Completes the Desktop UI bundle (M10 + M11).

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

docs/ROADMAP.md

@@ -37,9 +37,11 @@ Ubuntu + NVIDIA first; `.deb` distribution (see `DECISIONS.md`).
 - [ ] SMART integration (smartmontools if present)
 
 ## Phase 4 — Desktop UI & installer
-- [ ] M10 desktop GUI (PySide6: dashboard, log browser, report viewer, logger controls)
-- [ ] M11 tray / menu-bar applet (QSystemTrayIcon: live M1 readouts + Run Diagnostic +
-      supporting actions — D13)
+- [x] M10 desktop GUI (PySide6: dashboard w/ history graphs, logs, health, games, environment,
+      inventory, setup, notifications, share)
+- [x] M11 tray / menu-bar applet (`gui/tray.py`: live CPU/GPU temp + memory readouts, status
+      line, Run Diagnostic submenu per game, Open dashboard / Start-Stop recording / Snapshot /
+      Quit — D13; close-to-tray, `--tray` autostart). Needs a tray host (AppIndicator on GNOME).
 - [~] Guided diagnostic session (pick game → focused M3 capture → M4 scan → findings),
       shared by tray/GUI/CLI — *core + CLI + GUI done* (`core/diagnostic.py`, `rigdoctor
       diagnose start/status/finish`, and a **Run Diagnostic** button per game on the GUI Games