Add enable/disable across ECS scopes + @OnEnable/@OnDisable hooks

Three enable/disable statement scopes, each a reversible flag flip:
  - `disable P on e` / `enable P on e` — one property on one entity. Clears
    the has-flag so queries stop matching; field data persists in storage, so
    enable restores it untouched. @OnDisable(P)/@OnEnable(P) handler hooks run
    at the toggle point with the property bound by name.
  - `disable Model` / `enable Model` — @ME_<Model> global flag; the model's
    entities drop out of every query while disabled.
  - `disable Handler` / `enable Handler` — @HE_<Handler> global flag; the
    handler stops being called each phase while disabled.

Nothing is copied or freed — each toggle is one global store or one has-flag
store. Reduces entirely to existing ECS machinery (has-flags, kind filter,
per-phase call guards), so the data-oriented model is untouched.

New AST node S_TOGGLE; emit_toggle lowers it. Query {Model} filter now ANDs
@ME_; phase calls now guard on @HE_. Parser gains enable/disable statements
and @OnEnable/@OnDisable annotations.

Vocabulary: `on` promoted from RESERVED to CLAUSE (parser now dispatches on
it); enable/disable added as STMT keywords — synced across ludic_syntax.h,
the TextMate grammar, and LudicTokens.kt (check-vocabulary.py clean).

examples/toggle.ludic demonstrates all three scopes (prints 6 0 7 1 0);
test.sh smoke asserts it. Reseeded; C-free fixpoint holds; goldens identical.
Also: stop tracking tools/.idea/ (gitignored).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

.gitignore

@@ -15,3 +15,4 @@ tools/editors/jetbrains/build/
 
 # IntelliJ plugin SDK sandbox (tools/editors/jetbrains)
 .intellijPlatform/
+.idea