fix(auto-triage): avoid regex backtracking in classification parser

[RSO]

Summary

• Replace the classification parser's markdown code-fence regex with a linear scanner.
• Preserve parsing support for bare, json, and JSON fenced blocks while avoiding CodeQL's polynomial ReDoS risk.

Verification

N/A

Visual Changes

N/A

Reviewer Notes

• Addresses CodeQL alert 421 for js/polynomial-redos in services/auto-triage-infra/src/parsers/classification-parser.ts.
• Automated checks run locally: pnpm format, pnpm --filter kilo-auto-triage-worker typecheck, pnpm --filter kilo-auto-triage-worker lint.
• Autoreview was attempted twice with ~/.kilocode/skills/autoreview/scripts/autoreview --mode local, but the helper failed before reviewing with kilo engine failed (1): Error: Session not found.

[kilo-code-bot]

Code Review Summary

Status: 1 Issue Found | Recommendation: Address before merge

Overview

Severity	Count
CRITICAL	0
WARNING	0
SUGGESTION	1

Issue Details (click to expand)

SUGGESTION

File	Line	Issue
services/auto-triage-infra/src/parsers/classification-parser.ts	115–116	Stale comment references the now-removed regex

Other Observations (not in diff)

Issues found in unchanged code that cannot receive inline comments:

File	Line	Issue
services/auto-triage-infra/src/parsers/classification-parser.ts	115–116	Comment reads _"The regex with lazy quantifier can miss the final block in very large texts with many markers, so search backwards from the end instead."_ — the regex it refers to was just removed by this PR. The fallback logic itself (backward tail search) remains useful as a belt-and-suspenders catch for malformed or nested fences, but the stated rationale is now misleading. Consider updating the comment to explain the actual remaining risk (e.g. nested/embedded inside block content).

Correctness notes

The core fix is sound:

• The [\.s\S]*? lazy quantifier that drove the polynomial ReDoS is correctly eliminated.
• fenceInfo.trim() handles \r\n line endings for the opening fence — no regression there.
• The blockEnd guard when closingFence === 0 is harmless (text[-1] returns undefined, condition is false).
• Embedded triple-backticks in JSON string values could still cause an early close, but JSON.parse would fail and the parser moves on — same behaviour as the original regex.

Files Reviewed (1 file)

• services/auto-triage-infra/src/parsers/classification-parser.ts — 1 observation (stale comment, not in diff)

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_{Reviewed by claude-sonnet-4.6 · 191,618 tokens}

_{Review guidance: REVIEW.md from base branch main}