fix: improve DOCX fidelity and isolate branch scope

[developer0hye]

What changed

This PR isolates the DOCX fidelity work into a mergeable branch and improves Word rendering fidelity without pulling in unrelated mixed-worktree changes.

Why

The previous worktree contained DOCX improvements together with unrelated render and parser changes. This PR keeps only the DOCX-focused work so it can be reviewed and merged independently.

Key changes

• add DOCX section-aware flow handling with page setup, headers/footers, columns, and explicit page breaks between internal pages
• improve DOCX numbering and mixed nested list rendering
• preserve DOCX table fidelity details including repeating header rows, alignment, and default/override cell padding
• recover DrawingML and VML text boxes and render anchored floating text boxes through the shared IR and Typst generator
• keep non-DOCX parser changes limited to minimal shared-IR compatibility updates for table fields
• extend DOCX fixture traversal so text inside floating text boxes is covered by structure assertions
• remove unrelated image crop, SVG, and font-weight-inference changes from this isolated branch

Verification

• cargo fmt --all
• cargo test -p office2pdf --lib parser::docx::tests:: -- --nocapture
• cargo test -p office2pdf --lib render::typst_gen::tests:: -- --nocapture
• cargo test -p office2pdf --test docx_fixtures -- --nocapture

Related: #111