feat(stovepipe): add the record controller, advancing a queue's last-green bookmark on a successful build

[roychying]

Why?

buildsignal has been publishing to the record topic already, but nothing consumes it, so the topic accumulates and Queue.LastGreenURI is never set.

The visible consequence is cost: with the bookmark permanently empty, process.deriveBuildStrategy always returns BuildStrategyFull, so every validation is a full-repository build even when the delta is one commit.

What?

New stovepipe/controller/record. It consumes Record{id}, loads the request, and branches on the outcome buildsignal already stamped:

State	Behavior
succeeded	advance the bookmark
failed, cancelled	ack; no queue write
superseded	ack (unreachable — buildsignal never publishes it)
anything else	non-retryable invariant error

The advance is a CAS retry loop mirroring buildsignal's releaseBuildSlot, guarded by CompareRequestID: a candidate that is not strictly newer is skipped without a write, which also makes redelivery of the same request a no-op.

Also wires the stage into the example server: the record topic previously had no Subscription, and the controller is now registered alongside the others.

One deliberate deviation: greenness is read from request.State rather than a persisted validation fact, because the fact store does not exist yet. This will be resolved in follow up PR.

Test Plan

Issue