library: vendors/kb_text_shape + vendors/file_utils; modules/ffi/stb_truetype.sx retired

kb_text_shape (v2.10, JimmyLefevre) had been LOST from the sx tree —
ffi/stb_truetype.sx referenced repo paths that no longer existed (and
nothing runs glyph_cache, so the dangling unit never fired). The
trimmed copy returns from the m3te project as a proper vendor:
curated c/kbts_api.h decls over the full upstream header, README with
provenance, and examples/1627 pinning context + font creation so the
unit compiles and runs in-suite. file_utils (in-house asset-read
helper with the Android AAssetManager hook) gets the same unit shape.

modules/ffi/stb_truetype.sx is gone: glyph_cache imports the three
vendored units (stb_truetype, kb_text_shape, file_utils) directly.

library/vendors/kb_text_shape/README.md

@@ -0,0 +1,22 @@
+# vendors/kb_text_shape — OpenType text shaping for sx programs
+
+- Version: **v2.10** (version history at the top of the header)
+- Source: <https://github.com/JimmyLefevre/kb> (`kb_text_shape.h`)
+- License: zlib-style permissive (see the header's license block)
+- Files: `c/kb/kb_text_shape.h` (the full upstream single-header,
+  ~30k lines), `c/kb_text_shape_impl.c` (defines
+  `KB_TEXT_SHAPE_IMPLEMENTATION` and includes it), and
+  `c/kbts_api.h` — a hand-curated MINIMAL declaration header carrying
+  only the bound surface, so decl synthesis never parses the full
+  upstream header.
+
+`#import "vendors/kb_text_shape/kb_text_shape.sx"` resolves through
+the stdlib search paths; the implementation compiles once per machine
+through sx's object cache. Shape contexts, fonts, runs, and glyphs are
+opaque pointers on the sx side (modules/ui/glyph_cache.sx is the
+reference consumer; `examples/1627-vendor-kbts-shape-context.sx` pins
+context + font creation in the sx suite).
+
+To upgrade: replace `c/kb/kb_text_shape.h` with a newer upstream copy,
+extend `c/kbts_api.h` if the bound surface grows, update this file,
+and rebuild (the object cache keys on source bytes).