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/schedule_checks.rs

@@ -38,7 +38,7 @@ mod tests {
     /// ordering edge — add `.before`/`.after` (order matters) or
     /// `.ambiguous_with` (provably order-independent) at the registration
     /// site. When triage lowers the real count, lower this constant too.
-    const AMBIGUITY_BASELINE: usize = 198;
+    const AMBIGUITY_BASELINE: usize = 171;
 
     fn cluster_app() -> App {
         let mut app = App::new();