Route deployment receipts to PR-opening threads

[mberman84]

Summary

• bind each pull request to the trusted native thread that opened it and keep that ownership immutable
• route deploy intent, repairs, receipt monitoring, and final deployment receipts to that opening thread even when a coordinator authorizes deployment
• reject unowned PRs before writing deploy intent or labels instead of guessing the coordinator thread
• reject ownership claims for nonexistent or closed PRs and exclude controller-only actors
• release DeployBot v0.2.19 and pin runtime examples to the reviewed implementation commit

Root cause

DeployBot treated the provider and thread ID passed by the deployment-request caller as the source thread. A coordinator requesting several unrelated PRs therefore became the receipt destination for all of them.

Validation

• 221 Python tests passed
• Ruff passed
• source distribution and wheel build passed
• structured Codex autoreview clean after fixes for controller-only claims and future-PR preclaims