The dashboard's engine-availability health check only counted engines
this process started. A second launch (e.g. `pnpm dev dashboard`
alongside an already-running `fusion`) is correctly refused the
per-machine engine singleton lock, so its engine map stays empty and
the dashboard showed a false "engine not running" banner even though an
engine was live on the machine.
ProjectEngineManager now records projects whose singleton lock is held
by another process (via EngineAlreadyRunningError) and exposes
hasRunningEngine(), which the health endpoint consults so the banner
reflects machine-level truth. Reconciliation still retries so this
process takes over if the other exits, and the "refusing to start" log
fires once per project instead of on every 30s reconciliation tick.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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