test(ooxml): Sprint 22 - document.rs formatting, images, DrawingML coverage

Add 28 new tests (43 → 71 total) covering:
- Formatting edge cases (bold/italic val="0"/val="false")
- Image parsing (extent, docPr, anchor, wrap types)
- DrawingML shape handling (nested wsp/sp, cxnSp)
- Hyperlink edge cases (missing attrs, both attrs, formatted runs)
- Namespace attribute handling (get_attr_with_ns)
- Error handling (malformed XML, empty run filtering)
- Numbering edge cases (self-closing elements, invalid values)

Bug fix: val="0" and val="false" now properly checked in
self-closing <w:b/> and <w:i/> elements (Event::Empty handler).

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: alanbld