Carry runId on the worker socket #287

Part of #277

transport.py connects to /worker with no query string. The
backend treats a connect with no matching runId as a new run and wipes
messageBuffer and baselineStore.activeRun. Harmless for one process today, but
it is the reason accumulated run state cannot survive a reconnect, which blocks
Preserve and Rerun.

Acceptance criteria

The worker socket carries ?runId= using the shared
WORKER_WS_QUERY name. A second connect within one run preserves accumulated
state. A test asserts the query is present in the handshake.

Size: S.