Replaced my bash implementation with the user's provided snippet.
Key differences that fix the bad credentials issue on macOS:
1. Uses openssl enc -base64 -A instead of openssl base64
2. Uses jq -r -c . to strictly format the JSON header/payload
3. Explicitly wraps the RSA signature binary in b64enc.
Replaced generate_jwt.py with generate_jwt.sh using only openssl and
coreutils. Updated SKILL.md to remove the python fallback section and
use grep/cut for JSON parsing instead of python3.
The previous implementation had a stdin conflict -- it passed the PEM
key on stdin but also needed to pass the unsigned data on stdin. Now
that we take a file path, openssl reads the key from the file and gets
the data to sign from stdin.
Also removed the dead-code tempfile fallback and unused hashlib import.
Chris Farhood