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_set.md

@@ -0,0 +1,37 @@
+---
+id: fn-world_set
+name: world_set
+category: ecs
+kind: builtin
+tokens: world_set
+sig: world_set(target, property, field, value)
+tip: Write one field of a model instance by numeric id (reflection ABI).
+order: 50
+---
+
+<code>world_set</code> writes a single field of a model instance by numeric id — the id-based counterpart to an ordinary `position.column = …` assignment, used when the property is not known at compile time. You give the target instance, the property id (from `world_prop_id`), the field id (from `world_field_id`), and the new value; the value is stored just as a direct assignment would. It returns nothing. Together with `world_get`, `world_has`, and the resolver functions, it lets a mod or tool mutate any field on any instance generically, which is how the reflection ABI mirrors the compiled `query`/field access at runtime.
+
+Parameters:
+- `target` — the model instance to write to, an `entity` handle
+- `property` — the property id, from `world_prop_id`
+- `field` — the field id within that property, from `world_field_id`
+- `value` — the new integer value to store
+
+```ludic
+program WriteField {
+  property Position { column: int = 0, row: int = 0 }
+  model Player { Position }
+
+  handler Boot phase Start {
+    spawn Hero { Position { column: 0, row: 0 } }
+  }
+
+  handler Nudge phase Update {
+    let position_property = world_prop_id("Position")
+    let column_field = world_field_id(position_property, "column")
+    for (position) in query [Position, {Player}] {
+      world_set(self(), position_property, column_field, position.column + 1)
+    }
+  }
+}
+```