Build stamp via assets/build_info.json (reliable: same path as the catalog)

config/version didn't survive export cleanly. Instead checkpoint_ops writes
assets/build_info.json at build time (a plain JSON file, packed by the same
include_filter as the avatar catalog) and the menu + in-world HUD read it
with FileAccess. Shows 'build PC3 <commit>' so playtest reports say exactly
which build is running.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_015jtxAiu5dAW4WxCNdGkrkJ

.gitignore

@@ -11,3 +11,4 @@ Thumbs.db
 
 # Godot UID files (regenerated from path)
 *.uid
+assets/build_info.json