1. Quick command exec ran in the gateway process's full environment
without env sanitization or output redaction. A quick command like
"env" or "printenv" would leak all API keys, OAuth tokens, and
bot credentials to the messaging user.
Fix: apply _sanitize_subprocess_env() before exec and
redact_sensitive_text() on output before returning.
2. GatewayRunner._pending_messages was written on every interrupt
(lines 1331-1334) but never read or consumed anywhere. The actual
interrupt delivery uses adapter._pending_messages (a separate dict).
Removed the write-only accumulation to prevent unbounded growth.
f6736ced81