fix(sse): escape backslash in ChatGPT-web citation link text (#6569)

[brick30llc-ctrl]

What

markdownLinkText() (ChatGPT-web citation renderer) escaped [ and ] but not the backslash itself. A citation label ending in — or containing — a backslash therefore produced a broken Markdown link:

• Label Path C:\ → [Path C:\](url) — the trailing \ escapes the closing ], consuming the link's bracket.
• Label a\[b → [a\\[b](url) — the bare \ before [ corrupts the escaping.

Fix: escape the backslash first, then the brackets.

Why

This is the sole real issue among the CodeQL js/incomplete-sanitization alerts blocking the v3.8.47 release PR (#6569) — open-sse/executors/chatgpt-web/citations.ts:52 (2 of the 9 new alerts flagged on the large release diff). The remaining 7 CodeQL alerts on #6569 are false positives (SHA-256 used for a device-fingerprint UA header / cache key / display-label suffix — not credential hashing; .includes() in test-file assertions; and an errorResponse that already routes through sanitizeErrorMessage(), the known Rule #14 / ERROR_SANITIZATION.md precedent).

Test (TDD)

New tests/unit/chatgpt-web-citations-escape.test.ts — failing-then-passing:

• trailing backslash in the label
• backslash preceding a bracket (no bracket leak)
• bracket-only labels (regression guard — existing escaping preserved)
• plain labels pass through unchanged

node --import tsx/esm --test tests/unit/chatgpt-web-citations-escape.test.ts  → 4/4 pass
node --import tsx/esm --test tests/unit/chatgpt-web-citations.test.ts         → 3/3 pass (no regression)

ESLint clean on both changed files. (Pre-existing omniglyph typecheck errors are unrelated — identical on the base ref.)

[gemini-code-assist]

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[diegosouzapw]

Thanks for the fix and the clean TDD test — verified locally: reverting only the markdownLinkText() change (keeping your new test) makes 2/4 assertions fail with exactly the broken output described in the PR body ([Path C:\](url) losing its closing bracket), and restoring the fix brings it back to 4/4 with no regression on the existing chatgpt-web-citations.test.ts suite (7/7 total). Escaping the backslash before the brackets is the right order — it guarantees any run of N backslashes becomes an even 2N, so it can never leak past the ] escape. Confirmed this is complementary to #6635 (d76aa40), not a duplicate — that commit never touched backslash escaping.

One thing missing before merge: this repo aggregates the changelog via per-PR fragments in changelog.d/ (see changelog.d/README.md) rather than editing CHANGELOG.md directly. Could you add changelog.d/fixes/6944-<slug>.md with a one-line bullet crediting yourself? Happy to help if useful — otherwise this looks merge-ready once that's added.

[diegosouzapw]

Merged — escapes backslash before brackets in ChatGPT-web citation link text (7/7 tests green, added a changelog fragment). Thanks @brick30llc-ctrl! (Remaining red checks are pre-existing release-tip base-reds tracked in #6967, unrelated to this fix.)