fix(markdown_parser): reject link reference definition with trailing text after destination

[jfmcdowell]

Note

This PR was created with AI assistance (Claude Code).

Summary

The bare-destination loop in skip_destination_tokens continued past whitespace into non-title text, treating [label]: /url invalid as a valid link reference definition with destination /url invalid. Now the loop stops at the first whitespace boundary when followed by non-title content, correctly rejecting the line as a definition per CommonMark §4.7.

Test Plan

• just test-crate biome_markdown_parser — 78 passed
• just test-markdown-conformance — 652/652
• just f
• just l

Docs

N/A.

[changeset-bot]

⚠️ No Changeset found

Latest commit: a804b2c

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[codspeed-hq]

Merging this PR will not alter performance

✅ 28 untouched benchmarks
⏩ 228 skipped benchmarks¹

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_{Comparing jfmcdowell:fix/md-link-def-trailing-text (a804b2c) with main (35305c9)}

Footnotes

1. 228 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩

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ℹ️ Recent review info

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📥 Commits

Reviewing files that changed from the base of the PR and between 35305c9 and a804b2c.

⛔ Files ignored due to path filters (1)

• crates/biome_markdown_parser/tests/md_test_suite/ok/link_definition_edge_cases.md.snap is excluded by !**/*.snap and included by **

📒 Files selected for processing (1)

• crates/biome_markdown_parser/src/syntax/link_block.rs

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Walkthrough

The markdown parser's skip_destination_tokens function has been modified to simplify the lookahead termination logic for bare link destinations. Previously, the parser required three conditions to end destination parsing: detecting a potential title starter, having accumulated destination content, and observing a whitespace separator. The updated logic removes the title starter check, now terminating solely on the presence of destination content followed by a whitespace boundary, thereby treating any non-title text beyond that boundary as the end of the destination.

Suggested reviewers

• dyc3
• ematipico

🚥 Pre-merge checks | ✅ 2

✅ Passed checks (2 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title accurately describes the main fix: rejecting link reference definitions with trailing text after destination, which directly matches the changeset's core objective.
Description check	✅ Passed	The description is clearly related to the changeset, explaining the bug fix, its CommonMark §4.7 compliance, and test results, all consistent with the changes made.

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• Create PR with unit tests

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