[TheGreatAxios]

Closes CL-11889. Stacked on #34.

What changed

• Text runs: bold, italic, underline, strike, colour (theme name or hex), size, and a link to a URL (http/https/mailto, written percent-encoded) or to another slide. Plain strings still work anywhere runs do.
• Lists: bulleted or numbered, nested to 5 levels, styled from the master (indents, accent bullets, 1. / a. / i. numbering). Adjacent numbered lists are separated so each starts a new sequence.
• Validation, all with slide and path:
  • bad URLs and missing slide targets;
  • lists deeper than 5, checked without recursion (10,000 levels returns an issue, not a crash).
• Line breaks keep their run's formatting. Text boxes take their list style as a parameter, ready for free-form slides.

Verified

• lint, format:check, typecheck, test and pins:verify pass. The fixture covers every feature; identical bytes, well-formed parts and resolved relationships all pass.
• python-pptx readback: run properties, list levels and numbering, separator paragraphs, URL and slide link targets.
• Quick Look shows the formatting.
• Not verified: that adjacent numbered lists restart in real PowerPoint/Keynote. Quick Look ignores the separator, and no PowerPoint or Keynote is available here.
• Independent review; all findings fixed.

[linear-code]

CL-11889

[corbits-triage]

Triage: Pass

No changes needed from you. A maintainer will review this pull request.

Stacked on #34: only this pull request's own changes were checked.

Triage will approve, request review.

[corbits-triage]

Triage requests changes:

• Conventions: added code matches a code pattern

Nothing triage asked to change still fails, so this request no longer stands.