Retain resolved questions across integration follow-ups

[Vilin97]

Later integration rounds can return only new resolutions. Previously, final enforcement examined only the last round, so #396 incorrectly listed 64 questions answered in earlier rounds as unresolved. Keep an explicit ledger of valid accepted resolutions across calls, expose it to integration, and support explicit reopening when later evidence changes an answer. Unknown IDs never enter the ledger and cannot support approval.

Validation: all 385 Python tests pass; Ruff check/format and diff checks pass. Regressions cover incremental answers, explicit retractions, unknown IDs, and unknown retractions. Replaying saved responses from #385, #393, and #396 preserves the first two verdict tables and removes stale unresolved entries from #396 without any additional model calls; #396 still requires discussion for its remaining substantive concerns.

[greptile-apps]

Advisory cross-file review against Lean Pool's supervisory rubric. This is not by itself a significance, source-verification, or merge verdict.

The PR appears safe to merge; known obligations remain fail-closed while valid earlier resolutions persist across follow-ups.

Summary

• Maintains a ledger of valid resolutions for known obligations across source follow-ups.
• Allows earlier resolutions to be explicitly reopened and prevents unknown IDs from entering the accepted ledger.
• Documents the integration behavior and adds regression coverage for retention, reopening, and unknown IDs.

_{Reviews (1) · Last reviewed commit: "Keep accepted resolutions across review ..."}