Replace document-centric categories (prose/heading/code/label) with a
universal set that works across documents, code, and UI:
- title: headings, identifiers, labels, JSON keys
- annotation: comments, docstrings, captions, alt text
- content: paragraphs, list items, flowing text
- value: string literals, numbers, form values
- code: unparsed code blocks
- structural: keywords, operators, punctuation
Built-in extractors now produce title/content/code. All 6 categories
are available for custom parsers (e.g. tree-sitter).
Also adds inline code detection in Markdown: backtick spans within
prose lines are split into separate code/content segments.