refactor(engine): ambiguity burn-down batch 2 — SettingsResource cleared, 198 → 171

New SettingsMutation set: the per-frame settings mutators
(handle_volume_keys → record_window_geometry_changes →
persist_window_geometry_after_debounce) run as a deterministic chain
ordered before GameMutation, so every reader already after GameMutation
observes the current frame's settings transitively. The four readers
outside that ordering (modal enter-speed chain, focus-ring pulse, HUD
avatar, and the game plugin's pre-mutation chain) are ordered after the
set explicitly.

SettingsResource ambiguities: 21 → 0. Baseline ratchets 198 → 171.

Refs #143

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

solitaire_engine/src/ui_modal.rs

@@ -695,7 +695,8 @@ impl Plugin for UiModalPlugin {
                 advance_modal_enter,
                 paint_modal_buttons,
             )
-                .chain(),
+                .chain()
+                .after(crate::settings_plugin::SettingsMutation),
         );
         // Click-outside-to-dismiss is independent of the open
         // animation chain — it reads `just_pressed(Left)` and runs