Auto-detected flaky tests (merge-group) — review for quarantine

[github-actions]

Flaky-test detection (issue #1782) found the following candidates
for quarantine during a merge-group CI run:

# CORE-TREE (requires human review): tests/unit/hooks/pr-workflow-gate-batch-gc.test.ts
tests/unit/index-pr-workflow-session-lifecycle-2602.test.ts

To quarantine: append each line to the appropriate
scripts/ci/quarantined-tests*.txt file.

This issue was filed automatically by the flake-detection workflow.

[zaxbysauce]

This is auto-generated output from the flake-detection workflow introduced by #1782 — the body is produced verbatim by scripts/ci/detect-and-quarantine-flakes.sh, so it's an actionable quarantine-review task, not a product bug.

What the code review established:

• The # CORE-TREE (requires human review) prefix on tests/unit/hooks/pr-workflow-gate-batch-gc.test.ts comes from the script's rule C: anything under tests/unit/{scope,agents,hooks} is deliberately not auto-suggested for quarantine and must be reviewed by a human. Per the repo's testing guidance, genuine pre-existing failures go in the quarantine ledgers, but core-tree tests deserve a root-cause pass first (timing/sleep-based assertions, port contention, shared fixture state are the usual suspects in the hooks suite).
• tests/unit/index-pr-workflow-session-lifecycle-2602.test.ts is a standard quarantine-suggestion candidate and is not currently listed in scripts/ci/quarantined-tests.txt (nor the platform-specific ledgers), so nothing is being re-reported.

Recommended handling: confirm both files still exist and reproduce the flake locally first — I could not locate either path in the current checkout by content search, so they may have been renamed or removed since the merge-group run that produced this report. If confirmed flaky, append tests/unit/index-pr-workflow-session-lifecycle-2602.test.ts to scripts/ci/quarantined-tests.txt (choosing the macOS/Windows ledger instead if the flake is platform-specific); for the core-tree hooks test, either fix the instability or document why quarantine is appropriate before adding it.

Note for triage: this issue is one of a recurring series of auto-filed reports (#2718, #2724, #2730, #2743, …). They share only the generator's boilerplate — the flagged test lists appear to differ — so please don't bulk-close as duplicates without comparing the code blocks; they can, however, be batched into a single quarantine-ledger PR.