#21201: fix(compaction): repair tool_use/tool_result pairing after compaction

## Problem Session compaction can drop or move toolResult messages in ways that leave `tool_use` blocks without matching `tool_result` blocks (or leave free-floating tool results). Strict providers (Anthropic-compatible APIs, Cloud Code Assist) reject the next request with a 400. ## Fix After `session.compact()` completes, re-run `sanitizeToolUseResultPairing(session.messages)` (when transcript policy enables it) and replace session messages with the repaired transcript. This is a post-compaction safety net that complements pre-compaction truncation/repair. ## Testing - Compiles clean - Verified logic is a pure transcript transformation already used in other truncation paths. <!-- greptile_comment --> <h3>Greptile Summary</h3> Adds post-compaction tool pairing repair to prevent 400 errors from strict providers when `tool_use` blocks are left without matching `tool_result` blocks after compaction. The fix applies the existing `sanitizeToolUseResultPairing` function (already used pre-compaction at line 594) to repair the transcript after `session.compact()` completes. <h3>Confidence Score: 5/5</h3> - This PR is safe to merge with minimal risk - The fix reuses an existing, well-tested transcript repair function that's already applied pre-compaction. The conditional check matches the existing pattern (line 593-595), and the implementation is defensive (checks length > 0 before replacing). No new logic is introduced, only applying an existing safety net at an additional point in the flow. - No files require special attention _{Last reviewed commit: 2102876} <!-- greptile_other_comments_section --> _{(5/5) You can turn off certain types of comments like style [here](https://app.greptile.com/review/github)!} <!-- /greptile_comment -->