chore: stop tracking CLAUDE.md

The file is machine-specific rather than anything the project depends on:
the ARM64 box64 `aapt`/`aapt2` wrappers it documents live outside the repo,
and the rest is on-device working rules. Nothing in the tree links to it.

It stays on disk and is now ignored, so it keeps working locally without
riding along in the branch.

.gitignore

@@ -65,3 +65,7 @@ Thumbs.db
 
 # KSP
 .ksp/
+
+# Local agent notes: machine-specific build setup and on-device rules, not
+# anything the project itself depends on.
+/CLAUDE.md