1. Remove vestigial ZULIP_API_KEY requirement:
- /api/v1/server_settings is a PUBLIC endpoint (verified HTTP 200 with or without credential)
- No Zulip API key is required for this call
- If a future leg genuinely needs abiba-bot's key, it must prove it with a 200 from
/api/v1/users/me as abiba-bot and label itself degraded when it cannot
- Never fall back to the vault's shared ZULIP_API_KEY
2. Make failed sends exit non-zero:
- A degraded leg (no credential configured) must stay exit 0
- A failed send (attempted and failed) must exit 1
- This distinguishes 'not configured' from 'attempted and failed'
Test evidence:
- No-credential run: exit 0, digest still produced
- Wrong password: exit 1, labelled SMTP error
- grep -n ZULIP_API_KEY: only comment reference remains
root