Render cached TOC field results like Word

[JSv4]

Closes #427.

What changed

• derive cached TOC hyperlink presentation from the existing complex-field annotations
• remove only hyperlink color and underline inside a TOC result, preserving underlying TOC formatting
• keep an ordinary same-style hyperlink blue and underlined
• record the measured Word region (0 blue pixels) and update the corpus attribution
• replace the old heuristic fixture with an outer TOC field, nested PAGEREF fields, and a same-style control

Verification

• focused native cross-paragraph/nested-field regression
• 5/5 generated TOC geometry/presentation browser tests
• 46/46 Word-reference and ratchet validation tests
• filtered fields-and-tabs parity: 1/1 page, minor, SSIM 0.95942, ink F1 0.99868
• TypeScript typecheck
• .NET solution build
• WASM build (3303 KB Brotli, under 4096 KB budget)
• npm package-boundary audit