Address security review findings by adding explicit constraints to specs
and implementation specialist role:
Architectural constraints (spec updates):
- metadata does not propagate through OperationEnv::invoke() — fresh
HashMap for nested calls, closes the back-door leak channel where a
handler that puts a secret in metadata would leak it to children and
across from_call to remote nodes (ADR-014)
- Config reload must be authenticated/local-only — malicious reload =
root-equivalent privilege grant (config.md)
- from_call trust is transitive — scoped env bounds reachability, not
what the remote op does (operation-registry.md)
- Token entropy ≥128 bits — prefix is lookup aid not secret, offline
hash verification requires high-entropy tokens (auth.md)
Implementation constraints (auth.md security constraints section + role spec):
- OsRng for cryptographic nonces (AES-GCM IV reuse is catastrophic)
- CachedKey derives Zeroize/ZeroizeOnDrop (no secrets in freed heap)
- No unwrap()/expect() outside tests (poisoned lock recovery, not crash)
- Implementation specialist role spec updated with all four constraints
