library: vendors/stb_image + vendors/stb_truetype — stb ships with sx

The stb headers move from the repo-root vendors/ (resolvable only
with CWD = sx repo) into library/vendors/ following the sqlite
convention — bindings module + c/ sources + provenance README — so
'#import "vendors/stb_image/stb_image.sx"' (image v2.30 + image_write
v1.16) and '#import "vendors/stb_truetype/stb_truetype.sx"' (v1.26)
work from any consumer via the stdlib search paths. modules/ffi/stb.sx
dissolves into the stb_image vendor; modules/ffi/stb_truetype.sx keeps
its non-stb text-shaping companions and re-imports the vendored unit.
examples/1625 pins a deterministic in-memory BMP decode; examples/1626
pins font init + metric invariants against the system Helvetica.

library/modules/ffi/stb.sx

@@ -1,7 +0,0 @@
-#import c {
-    #include "vendors/stb_image/stb_image.h";
-    #source "vendors/stb_image/stb_image_impl.c";
-
-    #include "vendors/stb_image/stb_image_write.h";
-    #source "vendors/stb_image/stb_image_write_impl.c";
-};

library/modules/ffi/stb_truetype.sx

@@ -1,7 +1,10 @@
-#import c {
-    #include "vendors/stb_truetype/stb_truetype.h";
-    #source "vendors/stb_truetype/stb_truetype_impl.c";
+// Font stack for the ui modules: the sx-shipped stb_truetype
+// (vendors/stb_truetype/) plus the in-repo text-shaping companions
+// (file_utils, kb_text_shape — repo-root vendors/, not yet promoted
+// to the library).
+#import "vendors/stb_truetype/stb_truetype.sx";
 
+#import c {
     #include "vendors/file_utils/file_utils.h";
     #source "vendors/file_utils/file_utils.c";
 

library/modules/ui/glyph_cache.sx

@@ -4,7 +4,7 @@
 #import "modules/gpu/types.sx";
 #import "modules/gpu/api.sx";
 #import "modules/ffi/stb_truetype.sx";
-#import "modules/ffi/stb.sx";
+#import "vendors/stb_image/stb_image.sx";
 #import "modules/ui/types.sx";
 
 // Cached glyph data with UV coordinates into the atlas texture