Add OpenCode config, throttling, and atomic file events

[xnoto]

Summary

• Adds workspace OpenCode configuration for this repository with the MCP servers used in local development and review flows.
• Adds route-specific chatty throttling that delays bursty sender-to-agent-thread traffic while preserving ordering and isolating cooldowns per route.
• Adds throttle metrics plus targeted tests for helper logic, worker delivery timing, dropped-agent routing, session-agent behavior, and daemon integration.
• Fixes daemon file event handling so message/session/agent files finalized via temp-file + atomic rename are queued from watchdog move events, preserving cross-platform POSIX behavior while keeping direct create handling.

Testing

• uv run --extra dev ruff check .
• uv run --extra dev ruff format --check .
• uv run --extra dev pytest
• Live daemon test on this branch:
  • started uv run --extra dev agent-hub-daemon
  • coordinator session created/registered as coordinator (ses_1580...)
  • attached OpenCode test session created/oriented (ses_157f...) and received AGENT HUB: orientation
  • test agent registered as assigned id clever-bear
  • agent -> coordinator delivered LIVE_TEST_PING from live-test-agent
  • coordinator -> agent delivered LIVE_TEST_COORDINATOR_TO_AGENT
  • agent -> coordinator replied LIVE_TEST_AGENT_RECEIVED

Notes

• Coordinator bootstrap timed out waiting for an assistant READY response, then continued in best-effort mode; message injection/routing still worked both directions.