Fix desktop IME enter handling and gateway restart guards

[nickytod]

Summary

• Add shared desktop IME composition detection and use it for Enter handlers in composer, edit composer, rename, and onboarding inputs.
• Hard-block raw systemctl stop/restart of hermes-gateway services from inside gateway sessions, even with yolo or approvals off.
• Change generated systemd gateway units to KillMode=control-group and assert that generated units no longer use KillMode=mixed.

Fixes #37483
Fixes #37453
Fixes #37454

Verification

• PYTEST_DISABLE_PLUGIN_AUTOLOAD=1 /opt/homebrew/bin/python3.11 -m pytest tests/tools/test_approval.py::TestGatewaySystemctlRestartGuard tests/hermes_cli/test_gateway_service.py::TestGeneratedSystemdUnits::test_user_unit_avoids_recursive_execstop_and_uses_extended_stop_timeout tests/hermes_cli/test_gateway_service.py::TestGeneratedSystemdUnits::test_system_unit_avoids_recursive_execstop_and_uses_extended_stop_timeout -q -o 'addopts='
• npm run type-check --workspace apps/desktop
• npm run test:ui --workspace apps/desktop -- src/lib/ime.test.ts
• npx eslint src/app/chat/composer/index.tsx src/components/assistant-ui/thread.tsx src/app/chat/sidebar/session-actions-menu.tsx src/components/desktop-onboarding-overlay.tsx src/lib/ime.ts src/lib/ime.test.ts

[teknium1]

Thanks for the multi-surface fix. Current main already covers the primary composer and gateway-restart reports, but this branch still contains useful desktop sibling-path coverage.

Problems

• hermes_cli/gateway.py:2381 and :2416 change KillMode away from the current remediation. Current main intentionally retains KillMode=mixed in hermes_cli/gateway.py:2764/:2798 and reaps orphans through ExecStopPost plus gateway/cgroup_cleanup.py:1-12 (commit e551da6ddb39a712c93e6c48a16aa748e2c7bc95).
• The raw-restart approval guard is now redundant: tools/terminal_tool.py:2250-2271 blocks lifecycle commands before approval or execution, including force=True (commit 245b95b09470bb3887943122a7d0de5bf20da055).
• Two desktop files changed here no longer exist on main. The live edit composer is now apps/desktop/src/components/assistant-ui/thread/user-edit-composer.tsx; its Enter paths at :545 and :573 remain unguarded. Current rename and onboarding Enter handlers are likewise unguarded at session-actions-menu.tsx:329-336, onboarding/flow.tsx:82-88, and onboarding/index.tsx:642-664.

Suggested changes

• Salvage the remaining IME guards and tests onto those current desktop paths, while dropping the superseded gateway/systemd portions.

Automated hermes-sweeper review.

[teknium1]

Please do not change this to KillMode=control-group. Current main intentionally preserves KillMode=mixed and adds ExecStopPost=-...gateway.cgroup_cleanup to reap orphaned per-PID processes after shutdown; see hermes_cli/gateway.py:2764-2768 and gateway/cgroup_cleanup.py:1-12 (commit e551da6ddb39a712c93e6c48a16aa748e2c7bc95).