Render attribute syntax (key:: value)

Summary

Render Roam's attribute syntax Key:: Value with visual distinction — the key portion styled differently from the value. Attributes are widely used in Roam for structured data (metadata, properties, fields).

Roam web behavior: Text before :: renders as a clickable attribute name (acts like a page link). Text after :: renders normally but the attribute name has distinct styling.

TUI adaptation: Render the key portion in bold with a distinct color (e.g., bold cyan or bold yellow). The value portion renders with normal inline markdown parsing (links, tags, etc. still work).

Implementation hints

Parser

• src/markdown.rs:14 — render_spans() and render_spans_with_refs() are the entry points
• Add attribute detection at the line level before inline parsing:
  1. Check if the block text matches ^([^:]+):: (.+)$
  2. If yes: render key with attribute style, then parse value with normal inline parsing
  3. If no: proceed with normal parsing
• Important: :: can appear mid-block (e.g., after a TODO marker), so match from the first :: occurrence

Rendering

• Key: bold + distinct color (e.g., Style::default().fg(Color::Cyan).add_modifier(Modifier::BOLD))
• Separator ::: rendered as-is in dim style
• Value: parsed with existing render_spans() for full inline markdown support

Examples

Input	Rendered as
Author:: [[John]]	Author:: [John] (cyan link)
Status:: {{TODO}}	Status:: ☐
Tags:: #project, #active	Tags:: #project, #active (cyan tags)
Source:: https://example.com	Source:: https://example.com

Edge cases

• Multiple :: in one block → only first occurrence is treated as attribute separator
• :: inside code backticks → should NOT be treated as attribute
• Empty value (Key::) → render key only

Tests

• src/markdown.rs has extensive test coverage — add tests for attribute parsing
• Test: attribute with linked value, plain text value, empty value, :: inside code

Acceptance criteria

• Key:: Value renders with distinct key styling
• Value portion supports full inline markdown (links, tags, code, etc.)
• :: inside backtick code is not treated as attribute
• Tests cover all edge cases