feat(types): IVec2 + Rect 2D value types (#1)

Phase 1 of the fuller type-system proposal: two by-value spatial types
that lower to packed integers (no heap, copy like scalars).

- IVec2 — integer 2D vector, a pair of int packed into one i64, for tile
  and grid coordinates: make/zero/x/y/add/sub/scale/dot, the grid distance
  manhattan, equal, and to_vector (widen into the fixed-point Vector).
- Rect — axis-aligned rectangle, four Q16.16 fixed components packed into
  one i128, for HUD boxes and hitboxes: make/x/y/w/h, the derived
  right/bottom/center, and the contains (point) / intersects (overlap) tests.

Both are exact and deterministic, bit-identical on every platform. Vector
and Color already cover phase 1's other 2D primitives.

Wired end to end: emit_core llty (IVec2->i64, Rect->i128), emit_call
dispatch, the FRAGS list + reseeded seed, a selfhost test (types2d),
per-symbol docs + type pages + inventory, and the vocabulary/editor sync
(header, JetBrains, TextMate, LSP).

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

selfhost/backend/emit_call.ludic

@@ -114,6 +114,14 @@ function emit_ns_call(ns: pointer, meth: pointer, e: Node) -> Val {
     if is_vector_ns(meth) { return emit_vector_ns(meth, e) }
     perr(`unknown builtin Vector.{meth}`)
   }
+  if (ns == "IVec2") {
+    if is_ivec_ns(meth) { return emit_ivec_ns(meth, e) }
+    perr(`unknown builtin IVec2.{meth}`)
+  }
+  if (ns == "Rect") {
+    if is_rect_ns(meth) { return emit_rect_ns(meth, e) }
+    perr(`unknown builtin Rect.{meth}`)
+  }
   if (ns == "Duration") {
     if is_duration_ns(meth) { return emit_duration_ns(meth, e) }
     perr(`unknown builtin Duration.{meth}`)