fix(core): reap channels and streamline control dispatch

[LukasParke]

What

• reap idle channel state without dropping buffered values, waiters, senders, or live subscribers
• build one frozen loop-history snapshot per iteration
• replace random park jitter with deterministic step-id/iteration jitter
• inline dispatch only for the bare ephemeral in-memory subprocess adapter

Why

Per-delegation channels accumulated for the harness lifetime, loop snapshots recopied history for each predicate, random jitter made replay nondeterministic, and ephemeral in-memory dispatch paid a handle round trip with nothing durable observing it.

This semantically ports the item-11 portion of fork/port/openrouter-fixes commit 27ddda8e onto current names. It deliberately excludes #69 EventBroadcaster and generator-yield behavior.

Test plan

• 98 focused channel/control/subprocess tests pass
• core/types typechecks
• root lint
• sentrux check .
• sentrux gate .
• source worker full core suite — 1,462 pass
• clean-context Pi review; fixed parked-stream reap order and narrowed inline eligibility

Compatibility

The default ephemeral in-memory adapter may dispatch nested steps inline. Adapters with storage or custom hooks continue through spawn().

[vercel]

@LukasParke is attempting to deploy a commit to the Matt Apperson's projects Team on Vercel.

A member of the Team first needs to authorize it.

[LukasParke]

Agent: Code CI/structural/DCO are green where configured; remaining external red checks are compat with an empty upstream OPENROUTER_API_KEY and Vercel authorization. Where core CI is red, the only failure is the unrelated timing-sensitive executeRunCode retry-backoff test; affected local/full suites passed. I cannot rerun upstream Actions without admin rights.