feat: implement word-to-html-swift converter

[PsychQuantClaw]

Summary

Restore and finish word-to-html-swift as a proper Layer 3 converter in macdoc.

The current main branch only carries the package manifest / README / CLI wiring from the earlier merge, but the tracked converter source and tests are missing. This follow-up issue lands the actual converter implementation.

Conversion Requirements

• Input: .docx
• Output: HTML stream / .html
• Architecture: direct Word → HTML path to preserve semantics without Markdown hub loss
• Protocol: implement DocumentConverter with StreamingOutput

Layer 1 / Core Dependencies

• ooxml-swift for Word parsing
• common-converter-swift (DocumentConverter, StreamingOutput, ConversionOptions)

Implementation Notes

• Convert headings, paragraphs, blockquotes, code blocks, tables, lists, hyperlinks, footnotes, and inline formatting
• Support optional frontmatter and extracted figures directory
• Keep package independent under packages/word-to-html-swift/
• Ensure CLI command macdoc word-to-html works against the restored package source

Test Strategy

• Package-level tests for headings / lists / tables / hyperlinks / images / footnotes / inline formatting
• Verify HTML shell generation and figure extraction
• swift test inside packages/word-to-html-swift

[PsychQuantClaw]

Opened follow-up PR: #52