feat(stdlib): namespaced standard library (issue #2)

Implement the bulk of the namespaced-stdlib proposal (workshopsoft/ludic#2):
156 namespace methods across Math, Text, List, Ease, Collide, World, Net,
Sys, Save, Mem, extended Screen, Color functions, extended Random, and Time.
All deterministic fixed-point; self-hosting (C-free bootstrap fixpoint holds).

Compiler (selfhost/):
- Math.*: sqrt/sin/cos/tan/atan2/asin/acos (fixed-point runtime prelude —
  bit-by-bit isqrt, 256-entry interpolated sine table, Ross atan2), plus
  hypot/dist/dist2/deg_to_rad/rad_to_deg/posmod/wrap/ping_pong/snapped/
  move_toward/smoothstep/lerp/remap/sign/floor/ceil/round.
- Text.* (complete): upper/lower/trim/repeat/pad, split/join/replace,
  and the libc-backed queries.
- List.* (complete): insert/remove_at/remove/sort plus the earlier ops.
- Ease.* (in/out/in_out/back/bounce) and Collide.* (rects/point_rect/
  circles/rect_circle).
- Phase 3: World/Net/Sys/Save namespaced over the bare builtins (byte-
  identical IR) and Mem.* (bytes/words/copy/fill/peek/poke).
- Screen.* extended (line/circle/fill_circle/triangle/fill_triangle via new
  runtime primitives; sprite/sprite_scaled aliases), Color.* functions,
  Random.* (value/int/sign), Time.* (frame/delta/elapsed/now — new
  game-loop frame counter).
- Fix a lexer bug: fixed-point literals with >4 fractional digits overflowed.

Docs & tooling:
- 129 new per-symbol doc pages; gen.py made data-driven (namespaces
  discovered from the docs, no hardcoded list); new check-impl.py enforces
  that every implemented namespace method / keyword / type / phase has a
  doc page, wired into `x test-tools`. Document the previously-undocumented
  keywords (break/continue/where/entry/new/public + and/or/not tokens).
- LSP: namespaced signature help (ns_method_sig) covering every namespace.

Tests: 12 new self-host/regression tests + a golden render for the drawing
primitives. All suites green (selfhost 21, regression 45, tools 29).

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

docs/language/text/text-index_of.md

@@ -0,0 +1,30 @@
+---
+id: text-index_of
+name: Text.index_of
+category: text
+kind: namespace-method
+tokens: Text.index_of
+sig: Text.index_of(s, sub) -> int
+tip: The byte index of a substring, or -1 if absent.
+order: 6
+ns: Text
+member: index_of
+---
+
+Returns the zero-based byte index where <code>sub</code> first appears in <code>s</code>, or <code>-1</code> if it never does — so <code>Text.index_of("hello world", "world")</code> is <code>6</code>. Use it to locate a separator before slicing, or as a present-and-where test in one call: guard with <code>if idx >= 0</code>. It reports the first match only.
+
+Parameters:
+- `s` — the string to search
+- `sub` — the substring to locate
+
+```ludic
+program KeyValue {
+  var pair: str = "hp=42"
+
+  handler Parse phase Update {
+    let eq = Text.index_of(pair, "=")            # 2
+    let key = Text.slice(pair, 0, eq)            # "hp"
+    let value = Text.to_int(Text.slice(pair, eq + 1, Text.length(pair)))
+  }
+}
+```