runtime(ws): derive hello envelope from daemon runtime summary

[ToadAid]

Summary

• derive websocket hello envelope fields from the daemon-backed runtime summary
• stop reading node_id and runtime_started_at directly from the boot snapshot
• preserve websocket hello shape, backlog replay, and live event flow

Why

This tightens the websocket runtime truth seam by removing a direct boot-snapshot dependency for fields already present in the daemon-backed runtime summary.

Scope

Changed:

• src/mirror-service/runtime_events_ws.ts

Not changed:

• routing
• websocket protocol shape
• event ordering
• sync/status/daemon internals
• compat code
• adapter-boundary files
• tests, except verification only

Details

This patch:

• imports getMirrordaemonRuntimeState(...)
• derives:
  • node_id from runtime.node_id
  • runtime_started_at from runtime.runtime_started_at
• keeps the hello envelope shape unchanged

Verification

• pnpm vitest run src/mirror-service/mirror_service.test.ts -t "surfaces runtime websocket connect and disconnect events to live subscribers"
• pnpm vitest run src/mirror-service/mirror_service.test.ts -t "streams /mirror/runtime/ws with backlog, live events, and protocol messages"