ttf.c: glyph raster cache, fixed slots, no allocation (item 4.3.7d)

Punch list §25 item 4.3.7d complete. ttf_raster_cache_get() looks up
(font, codepoint, size_px) in a caller-owned fixed slot array, evicting
round-robin once full, rasterizing into a slot on a miss.

Verified live in tools/ttftest.c: an identical (font, 'A', 24px) call
made twice returns was_hit=0 then was_hit=1, and the slot's own hits
counter reads exactly 1 afterward -- checked programmatically. A
different-codepoint call misses again, proving the key actually
discriminates. Wall-clock timing (miss 0.040ms vs hit 0.001ms) is
printed as informational corroboration only, not the load-bearing
check.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

FABRIC.md

@@ -4849,11 +4849,36 @@ document and committing that amendment as its own item.*
   > job), but `ttf.c` builds into all three via the `hal/*.c` wildcard so a portability
   > compile check costs little and catches real bugs early.
 
-- [ ] **4.3.7d — Glyph raster cache.** Rasterizing on every draw call is too slow for
+- [x] **4.3.7d — Glyph raster cache.** Rasterizing on every draw call is too slow for
   repeated text; cache rasterized bitmaps keyed by (font, codepoint, size). *Done when:*
   drawing the same codepoint/size twice measurably hits the cache on the second call (e.g. a
   counter or timing difference), verified live, not just "code that should cache." *Refs:*
   §27.7.
+  > **Done 2026-08-10.** `ttf_raster_cache_get()`/`ttf_raster_cache_init()` in
+  > `src/starkernel/hal/ttf.c`/`ttf.h`: a fixed, caller-owned slot array (no allocation, same
+  > convention as the rest of this module), linear-scan lookup keyed by (font pointer,
+  > codepoint, size_px), round-robin eviction once every slot is full. Each slot is a fixed
+  > `TTF_CACHE_BITMAP_DIM` (80×80) square, rasterized at a fixed origin
+  > (`TTF_CACHE_MARGIN`, `size_px + TTF_CACHE_MARGIN`) regardless of the glyph's own bounding
+  > box — a caller doing real text layout (4.3.7e) needs to know this fixed convention, not
+  > assume the bitmap is tightly cropped to the glyph.
+  >
+  > **Verified live, not just "code that should cache"** (this item's own bar): extended
+  > `tools/ttftest.c`'s `test_raster_cache()` calls `ttf_raster_cache_get()` twice for the
+  > identical (font, `'A'`, 24px) key — first call returns `was_hit=0` (rasterized), second
+  > returns `was_hit=1` (cache hit), and the slot's own `hits` counter reads exactly 1
+  > afterward, checked programmatically, not just printed. A third call for a different
+  > codepoint (`'a'`) at the same size misses again, proving the key actually discriminates
+  > rather than the cache just always reporting "hit". Wall-clock `clock()` timing is also
+  > printed as corroborating evidence (miss 0.040ms vs. hit 0.001ms on this run) but is
+  > explicitly labeled informational-only in the test's own output, since host `clock()`
+  > resolution is coarse and this repo doesn't treat unverified timing claims as proof on
+  > their own — the hit counter is the load-bearing check.
+  >
+  > No kernel-boot/screendump verification needed — this item's own "done when" only asks
+  > for a measurable hit, which the host test above demonstrates directly; unlike 4.3.7c,
+  > nothing here is CANVAS-visual. Compile-checked clean (`-Wall -Werror -Wextra`) on all
+  > three architectures, with and without `-D__STARKERNEL__`.
 
 - [ ] **4.3.7e — `TTF-TEXT` entry point.** `TTF-TEXT ( c-addr u x y size color -- )`,
   analogous to 4.3.6f's `TEXT` but TrueType-backed — becomes the primary text-rendering path