Flaky: MarkdownRenderer 'unclosed verbatim openers in linear time' ratio reads 5.24 against a limit of 5 on a CI shard #18623

Flake ledger entry.

• Test: website/src/test/MarkdownRenderer.test.tsx > MarkdownRenderer LaTeX-native delimiters (#7803) > pairs thousands of unclosed verbatim openers in linear time (one pass, not a scan per opener)
• OS: ubuntu-latest, job Frontend Tests (1)
• Run: https://github.com/kirodotdev/KiroCrew/actions/runs/37986912372/job/114022810862 (on PR fix(stt): end dictation when Transcribe drops the stream #17925)
• Failing line: MarkdownRenderer.test.tsx:1951 — expect(ratio).toBeLessThan(5) got 5.241513827375625. 1 failed in that file (169 tests).

PR #17925 changes only the Transcribe branch of dashboard/stt_stream.py, its tests and the stt-streaming spec; it touches no frontend code.

Likely mechanism, not verified: the test compares the median render time at 6000 openers against 2000 openers. Its comment puts the linear-time ratio at about 2.5x and the quadratic one at about 7.5x, so the limit of 5 sits between them. A shard under load slowed the larger renders enough to push the ratio just past 5. A higher limit (still well under 7.5x) or more samples per size would reduce the chance of this.