Bug: TERMINAL_ENV in ~/.hermes/.env overrides terminal.backend in config.yaml

Summary

When a user switches terminal backends via hermes config set terminal.backend local (or by editing config.yaml directly), the change appears to take effect — hermes config show confirms terminal.backend: local — but the gateway, scheduler, and some agent sessions continue executing tools against the previously configured backend (e.g. docker). The root cause is a leftover TERMINAL_ENV=<backend> line in ~/.hermes/.env, but this wasn't set explicitly. Result is a flaky docker vs local backend behaviour.

This is a footgun specifically for users who set up Hermes with docker, then later switch to local.

Repro

1. Install Hermes, run setup with terminal backend = docker. .env ends up with TERMINAL_ENV=docker.
2. Later: hermes config set terminal.backend local (or edit config.yaml directly).
3. hermes config show → terminal.backend: local ✓
4. Restart the gateway. Restart the Mac. (Both done — no effect.)
5. Interact with hermes for 30mins
6. Send a message that triggers local access, agent's terminal tool call fails with:

   subprocess.CalledProcessError: Command '['/usr/local/bin/docker', 'run', '-d', '--init', ...

   because Docker Desktop isn't running.
7. Scheduled cron jobs hit the same error; daily digests silently fail or run in degraded mode.

Workaround

Manually edit ~/.hermes/.env and comment out the TERMINAL_ENV=... line, then restart the gateway.