Satisfies the repo-wide subprocess-stdin guard
(tests/tools/test_subprocess_stdin_guard.py); the long-lived bridge
child should not inherit the gateway's stdin.
Adds a Raft platform adapter as a bundled plugin (plugins/platforms/raft/)
connecting Hermes to Raft as an external agent via a wake-channel bridge.
The adapter starts a loopback HTTP endpoint, spawns 'raft agent bridge' as a
child process, and injects content-free wake hints into the gateway session
pipeline. The agent reads/sends messages through the Raft CLI; the adapter
never touches message bodies or delivery cursors. Activity observer hooks
report tool/LLM/session lifecycle events via a bounded at-most-once queue.
Auto-enables when RAFT_PROFILE is set.
Cherry-picked from PR #47629. Authored by skyzh (@xxchan).
