[codex] Refactor MQTT command handling reliability

[FireHawken]

Summary

Refactors command handling and runtime state to make the MQTT listener more reliable:

• adds AGENTS.md and updates README release/usage details
• moves sleep/monitor-off execution out of the MQTT callback into the main loop
• synchronizes shared runtime flags with Windows Interlocked* helpers
• validates command payloads and ignores retained command messages
• hardens Windows power actions with timeout/failure logging

Impact

Command topics now require an explicit payload: 1, true, on, or yes. Retained command messages are ignored to avoid accidental actions after reconnect.

Validation

• mingw32-make -C build

Notes

Local untracked files .gitignore and CLAUDE.md were not included.