Preserve deploy intent through integration conflicts

[mberman84]

Summary

• keep each exact-head deploy request discoverable while a cumulative integration PR is active or conflicted
• elect one active source thread to own conflict repair and point it at the cumulative PR
• recover original source requests automatically if the conflicted integration closes
• retain source intent through resume so late source-head changes cannot strand authorized work
• release DeployBot v0.2.16 and pin all runtime examples to the reviewed implementation commit

Validation

• PYTHONPATH=src python3 -m pytest -q (211 tests, 201 subtests)
• ruff check src tests
• python3 -m build
• structured Codex autoreview: clean