feat(displays): monitors w/ resolution+refresh in Inventory; flag sub-max refresh in Health — 0.39.0

New core/displays.py reads connected monitors via GNOME Mutter DisplayConfig over
D-Bus (busctl --json; works on X11 + Wayland), falling back to xrandr on other X11
desktops. Inventory's Display section now lists each monitor's resolution + current
refresh (e.g. 'DP-1 · Samsung LC34G55T: 3440x1440 @ 165 Hz'). System Health
(check_displays) flags a monitor running below its max refresh AT THE CURRENT
resolution (e.g. 165 Hz panel set to 60 Hz) — never suggests lowering resolution.
+tests (Mutter JSON + xrandr parsers, health check).

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

CHANGELOG.md

@@ -5,6 +5,17 @@ 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).
 
+## [0.39.0] - 2026-05-22
+### Added
+- **Displays in the Inventory.** A new `core/displays.py` lists each connected monitor with its
+  resolution and current/max refresh — e.g. `DP-1 · Samsung LC34G55T → 3440x1440 @ 165 Hz`. Reads
+  GNOME's Mutter `DisplayConfig` over D-Bus (works on X11 *and* Wayland), falling back to `xrandr`
+  on other X11 desktops.
+- **System Health flags monitors below their max refresh.** If a monitor supports a higher refresh
+  at its current resolution (e.g. a 165 Hz panel set to 60 Hz — an easily-missed gaming setting),
+  Health reports it with the fix (raise it in Display settings). Max is computed at the *current*
+  resolution, so it never suggests dropping resolution.
+
 ## [0.38.0] - 2026-05-22
 ### Added
 - **PCIe link in the Inventory.** Each NVMe drive now shows its negotiated PCIe link next to the