Preserve patch decisions across old and duplicate-marker histories

[rmcdaniel]

Outcome

Repair Python patch insertion into old histories and freeze one decision per change ID, while preserving existing consistent duplicate-marker histories and their physical cancellation boundaries.

Refs #103. Keep the issue open through published-artifact verification.

Qualification

• Old pending/completed activities choose the legacy patch branch without consuming or repeating their commands.
• One decision per change ID, with supported-range and version/patch-family checks on every call.
• Existing consistent duplicate markers replay as aliases, retaining their physical positions and committed cancellation boundaries. Conflicting decisions fail explicitly.
• 252 affected replay/cancellation/corpus tests pass. The full non-integration run passed 2,532 tests with two Git-dependent setup errors. Both checks pass separately in the Git-capable container. Ruff and mypy pass.
• Three new replay-corpus fixtures pass through the official replayer and all three fail against exact pre-fix source 04790ae42e8da0a83f65026f096572b547b7baa8. Corpus growth validation passes.
• Hosted Python 3.12 exposed an existing callback PID-file publication race. The fixture now publishes its PID by atomic rename, retaining all actual-process termination, heartbeat independence and stale completion assertions. No production worker shutdown behavior changes.
• Implementation head de92f1139acdbaa9e037351dd3c46931fbb0b6ef passes every normal hosted check, including integration and target-branch qualification.
• Untouched published Server 2.5.16, digest sha256:d0035cbffa5b904e5f9f7f43f84f6caf03beefc93bab8731c7e960b7a344e771, accepted original histories written by published Python 2.5.0. A distinct cold source-candidate worker completed both original runs once, preserving the unmarked branch and both retained duplicate markers. A new run with two patch calls completed with exactly one marker. The old process exited with code 137 before replacement. This is source qualification, with published successor verification still pending.
• Prepare patch release 2.5.1, paired with the actually exercised Server 2.5.16. Exact release-head checks and post-publication replay/consumer verification remain required.

Shared cross-SDK/embedded fixture changes remain coordinated with the Server #325 owner. This PR changes only the Python adapter and its own SDK corpus, with no Server or shared-runner edits.