Enhancement: expose richer pool status information

[ninan-nn]

Summary

PoolSnapshot currently exposes only a small set of fields:

• state
• idleCount
• lastError

This is not enough for debugging or operating a sandbox pool.

Proposal

Please expose a richer pool status API, either by expanding PoolSnapshot or adding a new model such as PoolStatus.

Useful fields would include:

• maxIdle
• borrowedCount
• running / stopped state
• primary / owner information in distributed mode
• state-store counters
• remote sandbox count
• richer reconcile / degraded diagnostics

A more complete status view would make pool behavior much easier to understand during acquire, warmup, failover, shutdown, and restart scenarios.