fix(parse/html/astro): accept astro files with empty frontmatter

[dyc3]

Summary

This PR allows the HTML parser to accept astro files that have frontmatter present, but it's empty. This was completely done using gpt 5.2.

fixes #7858

Test Plan

Added a new snapshot test.

Docs

[changeset-bot]

🦋 Changeset detected

Latest commit: 736113f

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 14 packages

Name	Type
@biomejs/biome	Patch
@biomejs/cli-win32-x64	Patch
@biomejs/cli-win32-arm64	Patch
@biomejs/cli-darwin-x64	Patch
@biomejs/cli-darwin-arm64	Patch
@biomejs/cli-linux-x64	Patch
@biomejs/cli-linux-arm64	Patch
@biomejs/cli-linux-x64-musl	Patch
@biomejs/cli-linux-arm64-musl	Patch
@biomejs/wasm-web	Patch
@biomejs/wasm-bundler	Patch
@biomejs/wasm-nodejs	Patch
@biomejs/backend-jsonrpc	Patch
@biomejs/prettier-compare	Patch

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[coderabbitai]

Walkthrough

This PR addresses Astro frontmatter parsing in Biome's HTML parser. The changes modify how empty frontmatter blocks are handled by converting silent parse result discarding into conditional node creation. When embedded content parsing returns Absent, the parser now explicitly constructs an ASTRO_EMBEDDED_CONTENT node. The fix includes a changelog entry and a test case validating that Astro files containing empty frontmatter (two --- delimiters) parse correctly.

Suggested labels

A-Parser, L-HTML

Suggested reviewers

• ematipico

🚥 Pre-merge checks | ✅ 4

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and specifically describes the main change: enabling Astro file parsing with empty frontmatter blocks.
Description check	✅ Passed	The description is related to the changeset, explaining the motivation (accepting Astro files with empty frontmatter) and referencing issue #7858.
Linked Issues check	✅ Passed	The PR successfully addresses issue #7858 by modifying the Astro parser to handle empty frontmatter blocks and includes a snapshot test validating the fix.
Out of Scope Changes check	✅ Passed	All changes are scoped to fixing empty frontmatter parsing: a changelog entry, parser logic modification, and a test case—nothing extraneous included.

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✨ Finishing touches

• 📝 Generate docstrings

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