fix bmad setup: create staging dirs without mode so _bmad is readable on Windows

mkdir(mode=0o700) yields an owner-only ACL on Windows with Python 3.13+,
leaving _bmad unreadable after the rename. Use the default mode instead.

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Sk72AxLwQnYttF6VFSxQLt

.agents/skills/bmad/scripts/render_skill.py

@@ -552,7 +552,7 @@ def _publish(destination: Path, outputs: dict[str, bytes], manifest: dict[str, A
     # for a name collision and tries the next name, some two billion times. The render
     # would hang in a folder it cannot write to instead of halting.
     staging = destination.parent / f".staging-{os.urandom(8).hex()}"
-    staging.mkdir(mode=0o700)
+    staging.mkdir()
     try:
         for name, content in outputs.items():
             path = staging / name