fix(ai-review): retain coverage after stale approval dismissal

[absorbb]

A normal follow-up push can trigger GitHub's dismiss_stale_reviews_on_push rule, changing a completed bot review from APPROVED to DISMISSED. The range selector ignored that completion marker and fell back to a full review. This happened on jitsu PR #1571, run 38911236256, despite an unchanged profile/merge base and just one descendant commit.

Accept valid completion markers from both APPROVED and DISMISSED trusted-bot reviews. Keep the marker version, reviewed commit ID, profile, merge base, ancestry, and different-head checks. Pending, commented, changes-requested, unmarked, or foreign reviews do not supply coverage. No prompt/profile changes are needed, so existing compatible markers remain usable.

Coverage records completed analysis independently of current merge approval. Dismissed reviews retain coverage even when dismissed manually; incremental: false explicitly requests a full review.

Validation: all 43 tests pass, with regression/negative cases for dismissed reviews; actionlint and git diff --check pass; fresh local review found no issues. Replaying the affected PR's pre-run review history with real Git ancestry selects full before the fix and incremental from cdec9ea to 2d9bef4 after it.

[jitsu-code-review]

Review of 7b77744a7feb64da29b359ab971d51f6592cfaff

Reviewed the complete diff and relevant coverage-selection and publication paths. No high-confidence defects found. All 33 relevant tests and git diff --check passed.