refactor(engine): ambiguity burn-down batch 4 — zero ambiguities, gate enforced

Clears the final 47 pairs and turns the ratchet into a hard gate
(AMBIGUITY_BASELINE = 0, assert_eq):

- HudButtons: the 14 HUD button/popover handlers run as one chain,
  before ui_focus::FocusKeys — Esc/keyboard consumption order is now
  defined (restore prompt → buttons/popovers → focus navigation →
  settings toggle) instead of scheduler-dependent.
- HUD text updaters (update_hud, update_selection_hud,
  update_won_previously) chained, in UiTextFx, after the new
  AutoComplete set (update_hud reads AutoCompleteState).
- restore_hud_on_modal → apply_hud_visibility chained before
  UpdateOnResize: HudVisibility writes, application, and the layout
  read happen in a fixed order.
- New writer sets UndoRequestWriters / InfoToastWriters (same
  self-ambiguous pattern as NewGameRequestWriters).
- Logic-before-paint: check_no_moves and the AutoComplete chain order
  before BoardVisuals; SettingsMutation after UpdateOnResize.
- MarkerVisuals set wraps the table painter chain; chrome fx declare
  disjointness from it.
- update_hud_typography after BoardVisuals; avatar/settings-toggle
  interaction handlers declared disjoint from HudButtons.

302 → 198 → 171 → 47 → 0 in four batches, one day. New systems now
fail CI unless they declare their ordering or their disjointness.

Closes #143

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

solitaire_engine/src/ui_modal.rs

@@ -699,7 +699,8 @@ impl Plugin for UiModalPlugin {
                 .after(crate::settings_plugin::SettingsMutation)
                 .in_set(crate::ui_theme::UiTextFx)
                 .ambiguous_with(crate::ui_theme::UiTextFx)
-                .ambiguous_with(crate::card_plugin::BoardVisuals),
+                .ambiguous_with(crate::card_plugin::BoardVisuals)
+                .ambiguous_with(crate::hud_plugin::HudButtons),
         );
         // Click-outside-to-dismiss is independent of the open
         // animation chain — it reads `just_pressed(Left)` and runs