Unify action-button states across the UI

- Add UiStyles with explicit normal, hover, pressed, focus and disabled styles and apply it to every action button.
- Disable timeline Previous/Next at the first/last event and keep Close always available.
- Style settings reset-dialog buttons and cover the button-state audit in docs/ui-copy.md.
- Add shared-state and timeline-boundary regression tests.

TODO.md

@@ -7,7 +7,7 @@ see `AGENTS.md` for the workflow and `MEMORY.md` for the decisions behind these
 
 Baseline: **v0.9.2** (2026-11-02). Three playable venues, tutorial/campaign/checkpoint resume,
 difficulty/help, audio/accessibility settings, a 24-NPC budget baseline, a complete
-escalation/access/radio loop, shift review, the Blender asset library, 258 headless + 97 Python
+escalation/access/radio loop, shift review, the Blender asset library, 259 headless + 97 Python
 tests, a clean screen-design judge and an optional Forward+ Desktop HQ build. This is a strong
 release-candidate foundation, not yet a 0.10.0 release candidate.
 
@@ -76,9 +76,11 @@ screen-design judge before any model/texture changes. No gameplay rules change.
 
 ### Button and panel behavior
 
-- [ ] Audit normal/hover/pressed/focus/disabled states on every button, including
+- [x] Audit normal/hover/pressed/focus/disabled states on every button, including
       tutorial skip, venue continue, settings apply/cancel/reset, judge/review,
-      radio send/emergency hold and Help close.
+      radio send/emergency hold and Help close. (Shared `UiStyles` states applied;
+      timeline boundary disabling and the keyboard-only F1 skip are documented in
+      `docs/ui-copy.md`.)
 - [ ] Verify keyboard-only and gamepad-only navigation: focus order, wrapping,
       default focus, confirm/cancel behavior and no focus traps.
 - [ ] Verify every modal closes with Esc/right-click where documented, recaptures