fix(worker): persist Architect provider snapshots

[Joncallim]

Summary

This child fixes the Architect provider snapshot contract exposed by the R3B adoption proof. The selected provider configuration is captured once and reused for model resolution and agent-run persistence. Model resolution observes the lease abort signal and fails closed if the provider changes.

The workflow also gives queue-adoption tests a pristine cloned PostgreSQL database, keeping their mutable fixtures separate from the mandatory S4 PostgreSQL proof database.

Stacked position

PR #302 is stacked on PR #301:

• Base branch: codex/pr198-producer-5a2-r3b-fence
• Base head: 7f36190940bd31d12ab0dcb63fe0a61bb05e16ae
• This child head: eb8cda2047d2f1dda45ded8028e0ec4364b42c69
• Scope: the provider snapshot implementation/tests plus the isolated queue-adoption workflow proof

Validation

• Web CI: run 30466426865, job 90625231841
• PR Contract Check: run 30466426572, job 90625230886
• GitGuardian: check 90625188717
• Unit suite: 1,722 passed across 117 files, zero skipped
• Queue-adoption task/answer/approval adoption markers passed
• Mandatory S4 PostgreSQL: 14/14 passed
• Mandatory Redis scrub: 3/3 passed
• Mandatory Redis ACL: 3/3 passed
• Production build, S3 concurrency (16), disabled ingress (1), and E2E (17 passed) passed

This is child-level evidence only. It does not claim that PR #301 or PR #198 is release-ready.