capsules/fonts: JetBrainsMono-Regular.ttf as a raw-blob capsule (item 4.3.7b)

mkcapsule.c already ingests arbitrary non-.4th files as raw byte blobs
(validate_forth_blocks only applies to .4th filenames), so no hex/base64
text-encoding or tool changes are needed -- corrects the design premise
in FABRIC.md's 4.3.7b item text (see the FABRIC.md correction note this
commit carries). ttf_load_from_capsule() resolves the font capsule by
name, validates its content hash, and points ttf_font_t at the capsule
arena bytes directly, zero-copy.

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

src/starkernel/hal/ttf.c

@@ -521,4 +521,39 @@ int ttf_glyph_outline(const ttf_font_t *font, uint32_t glyph_index, ttf_outline_
     out->point_count = 0;
     out->contour_count = 0;
     return decode_glyph_r(font, glyph_index, out, 0);
-}
+}
+
+/* ===========================================================================
+ * 4.3.7b — font data ingestion (capsule-backed, zero-copy)
+ * ===========================================================================
+ */
+
+#ifdef __STARKERNEL__
+
+int ttf_load_from_capsule(
+    const CapsuleDirHeader *dir,
+    const CapsuleDesc *descs,
+    const CapsuleNameEntry *names,
+    const uint8_t *arena,
+    const char *capsule_name,
+    ttf_font_t *out) {
+    const CapsuleDesc *cap;
+    const uint8_t *payload;
+    CapsuleValidateResult vr;
+
+    if (!dir || !descs || !names || !arena || !capsule_name || !out)
+        return TTF_ERR_BAD_TABLE;
+
+    cap = capsule_find_by_name(dir, descs, names, capsule_name);
+    if (!cap) return TTF_ERR_TABLE_MISSING;
+
+    vr = capsule_validate(cap, arena, dir->arena_size, 1);
+    if (vr != CAPSULE_VALID) return TTF_ERR_BAD_TABLE;
+
+    payload = capsule_get_payload(cap, arena);
+    if (!payload) return TTF_ERR_BAD_TABLE;
+
+    return ttf_parse(payload, (uint32_t) cap->length, out);
+}
+
+#endif /* __STARKERNEL__ */