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/builtins/fn-file_write.md

@@ -0,0 +1,29 @@
+---
+id: fn-file_write
+name: file_write
+category: builtins
+kind: builtin
+tokens: file_write
+sig: file_write(handle, buf, len)
+tip: Write a run of raw bytes to a stream handle.
+order: 50
+---
+
+Writes <code>len</code> bytes from <code>buf</code> to the given stream <code>handle</code>. Get the handle from <code>file_stdout</code> or <code>file_stderr</code>; the buffer is typically a string (whose length you pass with <code>len(buf)</code>) or a raw buffer from <code>bytes</code>. This is the precise, no-frills output primitive that underpins Ludic's own tooling and code generators, where exact bytes matter and the automatic newline of <code>print</code> would get in the way. Pass a byte count that does not exceed the buffer's size.
+
+Parameters:
+- `handle` — a stream handle from `file_stdout` or `file_stderr`
+- `buf` — the bytes to write (a string or a raw buffer)
+- `len` — how many bytes to write
+
+```ludic
+program WriteTwice {
+  handler Emit phase Start {
+    let out = file_stdout()
+    let heading = "SCORE: "
+    let value = "250\n"
+    file_write(out, heading, len(heading))
+    file_write(out, value, len(value))
+  }
+}
+```