Two concurrency bugs identified in PR #2904 review:
1. Replace sync.WaitGroup with sync.Cond-based activeReqCount to avoid
the "WaitGroup is reused before previous Wait has returned" panic that
occurs when Add(1) races with a goroutine-launched Wait().
2. Make panic cleanup conditional: when runTurn panics, only delete the
session's activeTurnStates entry if it still points to our placeholder.
Previously, an unconditional delete could wipe a new message's slot
claimed between the panic and the deferred cleanup.
Add a non-blocking runtime publish path and switch hot-path publishers to it.
Enforce subscription timeout boundaries, keep ordered subscriber snapshots up to date on subscribe changes, expose all runtime kinds to process hooks, add safe log attrs for non-agent events, and close the gateway message bus on full shutdown.
SiYue-ZO