refactor(markdown-parser): promote blank lines between list items to MdNewline nodes

[jfmcdowell]

Note

AI Assistance Disclosure: This PR was developed with assistance from Claude Code.

Summary

• Add AnyMdBulletListMember = MdBullet | MdNewline union to the grammar, so MdBulletList can hold both item nodes and blank-line nodes as children.
• Change MdBulletList from MdBullet* to AnyMdBulletListMember*.
• Update skip_blank_lines_between_items to emit explicit MdNewline CST nodes instead of calling parse_as_skipped_trivia_tokens.
• Update to_html.rs ordered list start extraction to use iter().find_map() to unwrap AnyMdBulletListMember::MdBullet (replacing direct .first() call).
• Regenerate formatter codegen for AnyMdBulletListMember (no manual formatter changes).
• Add test fixture for blank lines between list items (bullet, ordered, multiple blank lines, mixed tight/loose).
• Update all list parser snapshots to reflect the new CST shape.

This is the follow-up to #9274. skip_blank_lines_between_items was the last remaining skipped-trivia call site for blank lines in list parsing. Each inter-item blank line is now a real MdNewline CST node visible to the formatter harness.

No user-facing behavior change. Parsed semantics and CommonMark conformance are preserved (652/652); only the internal CST representation changes.

Test Plan

• cargo test -p biome_markdown_parser — 131 tests pass (63 + 68)
• cargo run -p xtask_coverage -- --suites=markdown/commonmark — 652/652 (100%)
• cargo check -p biome_markdown_formatter — compiles cleanly
• just l — lint passes
• Snapshots verified: MdNewline nodes appear between MdBullet siblings in loose lists; tight lists have no MdNewline between siblings

Docs

N/A — internal structural change, no new user-facing features.

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📥 Commits

Reviewing files that changed from the base of the PR and between fb05546 and f2c5204.

⛔ Files ignored due to path filters (4)

• crates/biome_markdown_factory/src/generated/node_factory.rs is excluded by !**/generated/**, !**/generated/** and included by **
• crates/biome_markdown_factory/src/generated/syntax_factory.rs is excluded by !**/generated/**, !**/generated/** and included by **
• crates/biome_markdown_parser/tests/md_test_suite/ok/list_blank_lines_between_items.md.snap is excluded by !**/*.snap and included by **
• crates/biome_markdown_syntax/src/generated/nodes.rs is excluded by !**/generated/**, !**/generated/** and included by **

📒 Files selected for processing (8)

• crates/biome_markdown_formatter/src/generated.rs
• crates/biome_markdown_formatter/src/markdown/any/bullet_list_member.rs
• crates/biome_markdown_formatter/src/markdown/any/mod.rs
• crates/biome_markdown_parser/src/syntax/list.rs
• crates/biome_markdown_parser/src/syntax/mod.rs
• crates/biome_markdown_parser/src/to_html.rs
• crates/biome_markdown_parser/tests/md_test_suite/ok/list_blank_lines_between_items.md
• xtask/codegen/markdown.ungram

🚧 Files skipped from review as they are similar to previous changes (7)

• crates/biome_markdown_parser/src/syntax/list.rs
• crates/biome_markdown_formatter/src/markdown/any/bullet_list_member.rs
• crates/biome_markdown_formatter/src/markdown/any/mod.rs
• crates/biome_markdown_parser/src/to_html.rs
• xtask/codegen/markdown.ungram
• crates/biome_markdown_formatter/src/generated.rs
• crates/biome_markdown_parser/tests/md_test_suite/ok/list_blank_lines_between_items.md

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Walkthrough

This change makes blank lines between list items explicit in the CST by adding a new union AnyMdBulletListMember = MdBullet | MdNewline, updates the parser to emit MdNewline nodes between bullets, extends to_html to locate MdBullet through the new union, adds a generated formatter FormatAnyMdBulletListMember plus AsFormat/IntoFormat impls and a pub(crate) bullet_list_member formatter module, and adds tests exercising blank lines between list items.

Possibly related PRs

• refactor(markdown-parser): promote list structural tokens from skipped trivia to explicit CST nodes #9274 — Alters list CST/formatting and list marker/prefix tokens; touches the same list formatting and parser paths.
• refactor(markdown): split list item parser #9167 — Modifies list parsing behavior in src/syntax/list.rs (blank-line and item continuation handling).
• feat(parser/markdown): parser implementation #8525 — Introduces/adjusts AnyMdBulletListMember-like grammar and integrates parser/formatter changes.

Suggested reviewers

• ematipico

🚥 Pre-merge checks | ✅ 2

✅ Passed checks (2 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and specifically describes the main refactoring: promoting blank lines between list items from trivia to explicit MdNewline CST nodes.
Description check	✅ Passed	The description is well-detailed and directly related to the changeset, outlining the grammar changes, parser updates, formatter codegen, tests, and verification steps.

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[ematipico]

Seems there's a conflict to solve

[jfmcdowell]

Seems there's a conflict to solve

@ematipico resolved