refactor(gui): grouped navigation + clearer page names — 0.20.0

Reshape the IA so it reads by intent instead of a flat pile of pages.

- Grouped sidebar: Monitor / Diagnose / System / App (section headers).
- Renames: Health → System Health, Environment → Tuning, Logs → Recordings,
  Setup → Settings.
- Settings absorbs Notifications (alerts) as a section; Notifications dropped as a
  separate page (notifications_page.py removed; SetupPage gains the alerts card +
  `changed` signal wired to the live alert monitor).
- Recordings is now a hub: a source dropdown to view any captured log (always-on /
  last diagnostic / preserved crash) + Analyze-crash in place, plus the recorder
  controls; status line now shows the captured game.
- main_window nav is data-driven (_NAV groups → _PAGES order → stack); show_page,
  badges, and tray flows updated. GUI smoke test asserts the new page set.

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

CHANGELOG.md

@@ -5,6 +5,19 @@ All notable changes to RigDoctor are recorded here. Format follows
 (`MAJOR.MINOR.PATCH`, pre-1.0). `__version__` and `pyproject.toml` must match the git
 release tag (so the auto-updater, D18, can compare versions).
 
+## [0.20.0] - 2026-05-22
+### Changed
+- **Reorganized navigation** into grouped sidebar sections — **Monitor** (Dashboard) ·
+  **Diagnose** (Games, Recordings, System Health, Tuning) · **System** (Inventory) · **App**
+  (Settings, Share) — so it's clear where to go.
+- **Renames for clarity:** *Health → System Health* (it's the overall 7-day system scan, not
+  per-game), *Environment → Tuning* (gaming tunables + fixes), *Logs → Recordings*,
+  *Setup → Settings*.
+- **Settings** absorbed **Notifications** (alerts) — app configuration (components/deps, alerts,
+  account access, uninstall) now lives in one page; Notifications is no longer a separate item.
+- **Recordings** is now a hub: pick which captured log to view (always-on capture, last
+  diagnostic, or a preserved crash), **Analyze crash** in place, alongside the recorder controls.
+
 ## [0.19.0] - 2026-05-22
 ### Added
 - **System-tray applet (M11, D13).** A tray icon whose menu shows live **CPU / GPU temp** and