fix(format/html): break if >2 children, and at least one is not whitespace sensitive

[dyc3]

Summary

This fixes formatting for the following snippet:

-<div>a<div>b</div> c</div>
+<div>
+  a
+  <div>b</div>
+  c
+</div>

Admittedly, it's not an ideal fix. The ideal fix would involve treating display: none as externally whitespace sensitive.

fixes #4927
fixes #6407

Test Plan

Improved prettier snapshots
Added some of our own snapshot tests

Docs

[changeset-bot]

🦋 Changeset detected

Latest commit: 997299f

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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[codspeed-hq]

Merging this PR will not alter performance

✅ 3 untouched benchmarks
🆕 1 new benchmark
⏩ 152 skipped benchmarks¹

Performance Changes

	Benchmark	BASE	HEAD	Efficiency
🆕	html_analyzer[index_1033418810622582172.html]	N/A	398.2 µs	N/A

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_{Comparing dyc3/html-force-break-nontext-and-blocklike (997299f) with next (cb112ce)}

Footnotes

1. 152 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. ↩

[coderabbitai]

Walkthrough

This PR fixes HTML formatter whitespace handling for block-like elements. The changes enhance the formatting logic in element_list.rs to correctly handle scenarios where block-like elements appear adjacent to text nodes. When multiple children exist and at least one is block-like, the formatter now emits hard line breaks and sets appropriate flags. Updates include CSS display utility comments, new test cases, and a changelog entry documenting the behaviour change.

Possibly related PRs

• fix(format/html): preserve whitespace between a HtmlSingleTextExpression/HtmlElement and HtmlContent #8595 – Modifies element_list.rs whitespace and line-break handling between elements and adjacent text content in the HTML formatter.
• fix(html): fmt svelte children #8539 – Restructures the element list API and behaviour in FormatHtmlElementList that this PR's whitespace-handling logic builds upon.

Suggested reviewers

• ematipico
• chansuke

🚥 Pre-merge checks | ✅ 4

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title accurately describes the main change: forcing breaks when elements have more than two children and at least one is not whitespace-sensitive.
Description check	✅ Passed	The description provides clear motivation with before/after code examples, links to fixed issues (#4927, #6407), and explains the test plan and limitations.
Linked Issues check	✅ Passed	The PR implements the core fix for both linked issues by correcting HTML formatter behaviour when handling whitespace-sensitive elements, as demonstrated by the updated formatting of a b c .
Out of Scope Changes check	✅ Passed	All changes are focused on the HTML formatter's whitespace handling. The changelog entry, skill documentation, and test files are all directly related to the fix scope.

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✨ Finishing touches

• 📝 Generate docstrings

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