The 5-minute reconciliation read the multi-GB OpenCode store on the hub's
event loop with bun:sqlite; a cold scan froze every request for ~88s and
stalled each machine's runner the same way.
- scan in a spawned `hapi usage-scan` child process (stdin/stdout JSON)
- refresh on demand from the usage page (debounced) + a daily fallback
- a runner whose hub is localhost skips the store the hub already owns
- machine scans run every 30min and read the message table sequentially
in one pass instead of per-session indexed lookups
