docs(api): per-symbol pages, fuzzy search, deep token linking, hover cards

Rebuild the API Reference around one page per symbol and richer, verified content.

Pages & navigation
- One HTML page per symbol (kw-*, type-*, phase-*, screen-*, fn-*, annot-*, op-*)
  instead of a single scrolling page; namespace overview pages (ns-screen …
  ns-color) and a searchable index (api.html) with client-side fuzzy search.
- Sticky-header scroll offset (scroll-margin) so a jumped-to entry/param/color is
  never hidden, plus a flash highlight on the scrolled-to target.

Deep linking in every snippet & example
- Namespace members split: `Screen`→namespace page, `fill_rectangle`→method page;
  `Color`→palette page, `Charcoal`→its swatch — separately.
- Named arguments (`width:`) link to that parameter's anchor on the method page.
- Hover any token for a summary card built from the real API data (symbols.json).

Content & coverage
- Full authoritative surface documented from the compiler: every keyword, type,
  the 6 phases (Start/Input/FixedUpdate/Update/LateUpdate/Render, each its own
  page), all 22 annotations, namespace methods with parameter docs, builtins,
  the world_* reflection ABI, networking, operators — 155 symbols.
- Longer, clearer explanations; "model"/"model instance" terminology, not "entity";
  descriptive identifiers in every example (Position{column,row}, Velocity{delta_x,
  delta_y}, Health{current,maximum}, Player/Enemy) — no Pos/Seg/x/dx.
- Accuracy fixes from compiler ground-truth: world_count() takes no arg,
  world_query_next(property, cursor) arg order, event fields bind by name; dropped
  `when` and `module` (not in the self-hosted parser).

Tooling
- inventory.json + check.py: coverage guard (every symbol has a page), duplicate-
  token guard, and broken-link guard — fail CI so docs can't drift.
- validate.py: compiles every ```ludic example against bin/ludicc (158 compile).

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

docs/language/ecs/fn-world_has.md

@@ -0,0 +1,35 @@
+---
+id: fn-world_has
+name: world_has
+category: ecs
+kind: builtin
+tokens: world_has
+sig: world_has(target, property) -> bool
+tip: Test whether a model instance currently carries a property.
+order: 50
+---
+
+<code>world_has</code> tests whether a model instance currently carries a given property, returning a boolean. It is the reflection-ABI equivalent of the membership test a `query` performs implicitly, and the safe guard to run before a `world_get`/`world_set` on a property an instance might not have. A property that has been `disable`d reads as absent here (its has-flag is clear), while one that is merely present with default values reads as present. Pass the target instance and the property id from `world_prop_id`.
+
+Parameters:
+- `target` — the model instance to test, an `entity` handle
+- `property` — the property id, from `world_prop_id`
+
+```ludic
+program CheckProperty {
+  property Position { column: int = 0, row: int = 0 }
+  property Shield   { amount: int = 0 }
+  model Player { Position, Shield }
+
+  handler Boot phase Start {
+    spawn Hero { Position { column: 1, row: 1 }; Shield { amount: 2 } }
+  }
+
+  handler Inspect phase Update {
+    let shield_property = world_prop_id("Shield")
+    for (position) in query [Position, {Player}] {
+      if world_has(self(), shield_property) { Screen.status("shielded") }
+    }
+  }
+}
+```