feat(docs): Render argparse metadata as semantic definition list

[tony]

Summary

• Replace inline pipe-separated metadata (Default: None | Type: str | Required) with semantic <dl> definition list structure
• Enable independent CSS styling of keys, values, and tags
• Use Furo's guilabel pattern for "Required" tag with semi-transparent amber background
• Support both light and dark mode with proper contrast
• Standardize all argparse elements to use var(--code-font-size) for consistent sizing

Changes

HTML structure (before):

<p class="argparse-argument-meta">Default: <span class="nv">None</span> | Type: str | Required</p>

HTML structure (after):

<dl class="argparse-argument-meta">
  <div class="argparse-meta-item">
    <dt class="argparse-meta-key">Default</dt>
    <dd class="argparse-meta-value"><span class="nv">None</span></dd>
  </div>
  <div class="argparse-meta-item">
    <dt class="argparse-meta-key">Type</dt>
    <dd class="argparse-meta-value"><span class="nv">str</span></dd>
  </div>
  <dt class="argparse-meta-tag">Required</dt>
</dl>

Font size standardization:

• CLI inline roles (.cli-option, .cli-metavar, etc.)
• Usage blocks (pre.argparse-usage)
• Argument names (.argparse-argument-name)
• Metadata elements (.argparse-meta-key, .argparse-meta-value, .argparse-meta-tag)

All now use var(--code-font-size) (Furo's 81.25%) for consistency with other code elements.

Test plan

• All 1017 tests pass
• Docs build successfully
• Visual verification at /cli/edit.html in light and dark modes

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 80.11%. Comparing base (3487e8b) to head (eacd727).
⚠️ Report is 9 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #1011   +/-   ##
=======================================
  Coverage   80.11%   80.11%           
=======================================
  Files          28       28           
  Lines        2409     2409           
  Branches      457      457           
=======================================
  Hits         1930     1930           
  Misses        356      356           
  Partials      123      123           

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