fix(cli): prefer active checkout for update banner

[MadKangYu]

Summary

• prefer the currently executing Hermes checkout when resolving update-banner git state
• keep ~/.hermes/hermes-agent as a fallback for default installs
• add split-runtime regression coverage so a stale contributor checkout cannot poison the banner
• fix the Linux systemd update-restart test to patch is_linux explicitly on macOS runners

Notes

• This PR is the correctness follow-up to fix(cli): add update check mode #7299.
• It matters when operators keep a clean runtime checkout and a separate contributor checkout under ~/.hermes/hermes-agent.

Testing

• cd /Users/yu/.hermes/hermes-agent-update-banner && /Users/yu/.hermes/hermes-agent/venv/bin/python -m pytest -q tests/hermes_cli/test_cmd_update.py tests/hermes_cli/test_update_check.py tests/hermes_cli/test_update_gateway_restart.py
• result: 43 passed

[MadKangYu]

Maintainer note: local targeted verification for this branch is green. Command run: pytest -q tests/hermes_cli/test_cmd_update.py tests/hermes_cli/test_update_check.py tests/hermes_cli/test_update_gateway_restart.py. Result: 43 passed. The failing GitHub test run looks like broader repo baseline instability (AIAgent.request_overrides, GatewayRunner._session_model_overrides, voice-mode/config-version failures) rather than a regression from this banner/runtime-correctness follow-up.

[alt-glitch]

Related to #11225 and #6330 — same update-banner checkout resolution issue.

[alt-glitch]

Related to #11225 and #6330.

[teknium1]

Thanks for the focused regression report. This is already implemented on main, so this PR is being closed as implemented.

• hermes_cli/banner.py:351-360 now resolves the executing checkout first and only falls back to $HERMES_HOME/hermes-agent when the runtime location is not a git checkout.
• hermes_cli/banner.py:372-383 applies the same ordering to banner git-state and release-tag resolution.
• Commit cca2869d78388e049ff1116e420b7209643a9c15 shipped this exact stale-profile-checkout fix; it is contained in release v2026.5.16.
• The member references to fix: use active checkout for update checks #11225 and fix(banner): prefer installed repo path in check_for_updates #6330 describe the same resolved checkout-selection behavior.

Automated hermes-sweeper review.