feat(gateway): restart manual profile gateways after update

[quocanh261997]

What

• Map running manual gateway processes back to Hermes profiles via each profile's gateway.pid file.
• During hermes update, relaunch profile-mapped manual gateways after terminating the old process.
• Keep the existing manual restart warning for gateway PIDs that cannot be mapped to a profile.
• Update the updating guide to describe service-managed and profile-mapped manual gateway restart behavior.

Why

hermes update already restarts service-managed gateways through systemd or launchd, including profile units. Manual profile gateways were only stopped, leaving users to run hermes -p <profile> gateway run or a profile wrapper restart by hand. This made multi-profile updates cumbersome and easy to leave half-refreshed.

How to test

scripts/run_tests.sh tests/hermes_cli/test_update_gateway_restart.py

Result: 42 passed.

Platforms tested

• macOS local test environment

Cross-platform impact

This touches process management. The change keeps the existing systemd and launchd service paths intact, and only adds a relaunch path for manual gateway processes that can be mapped through profile PID files. Unmapped manual processes keep the existing manual restart guidance.

[teknium1]

Merged via PR #18178 — your commit was cherry-picked onto current main with your authorship preserved in git log. We also added a small follow-up on top routing the manual profile restart through the graceful SIGUSR1 drain path (same one systemd/launchd services use) so in-flight agent runs drain instead of being SIGTERM'd. Thanks for the contribution!

#18178