fix(mdxish): fix rendering callout from magic blocks

[maximilianfalco]

	Fix RM-14652

🧰 Changes

Fixes an issue where callout magic blocks ([block:callout]...[/block]) were not rendering correctly in the mdxish pipeline. The placeholder tokens (__MAGIC_BLOCK_0__) are parsed as inlineCode nodes, which can end up inside paragraphs. When magic blocks create flow elements (like mdxJsxFlowElement), they need to be unwrapped from the paragraph to maintain valid AST structure.

Changes

• Magic block parser: Callout magic blocks now create mdxJsxFlowElement nodes directly with name 'Callout' instead of intermediate rdme-callout nodes
• Title conversion: Callout titles are converted to h3 headings to match calloutTransformer behavior
• Unwrapping logic: Added logic to unwrap mdxJsxFlowElement nodes from paragraphs in magicBlockRestorer, since flow elements cannot be children of paragraphs in MDAST

Before

Screen.Recording.2025-12-17.at.22.12.27.mov

After

Screen.Recording.2025-12-17.at.23.32.40.mov

🧬 QA & Testing

• Broken on production.
• Working in this PR app.

[kevinports]

Looks good to me. Noticed a few small things to be addressed but giving approval so this isn't blocked.