chore: remove 12 old exe from git + use git rm in cleanup

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

build.py

@@ -400,8 +400,19 @@ def cleanup_old_releases():
     keep = set([first] + last_5)
 
     removed = []
+    _flags = subprocess.CREATE_NO_WINDOW if sys.platform == "win32" else 0
     for f in all_exes:
         if f not in keep:
+            # Use git rm so deletion is staged for commit
+            try:
+                subprocess.run(
+                    ["git", "rm", "-f", "--quiet", f],
+                    cwd=PROJECT_DIR, creationflags=_flags,
+                    capture_output=True,
+                )
+            except Exception:
+                # Fallback: just delete the file
+                if os.path.exists(f):
                     os.remove(f)
             removed.append(os.path.basename(f))