v1.13.5: psrpc room-topic subscription goroutine/memory leak under high room churn

We are seeing continued goroutine and RSS growth on livekit-server v1.13.5 under high room churn.

After restart, the node returns to a healthy baseline around:

go_goroutines: ~10k–15k RSS: ~500 MB

After roughly 1–2 days of high churn, with only tens of active participants, it grows to approximately:

go_goroutines: ~200k–250k RSS: ~2.5–3 GB