fix(save): underline, strikeout and highlights on rotated pages run along the text (#527)

[DutchSailor]

Closes #527. Builds on #530 (Caret and Replace, #508 part 1): until #530 is merged, the diff of this PR includes its commit; the change of this PR itself is the last commit.

What happened

Text markups (Highlight, Underline, StrikeOut, Squiggly) were saved with each quad axis-aligned in user space in a fixed order, and without an appearance stream. Viewers build the appearance from the quads and take the edge from the first to the second point as the text direction, so on pages with /Rotate 90 or 270 underline and strike lines were drawn across the text as short marks.

What this changes

• js/pdf/saver/text-markup-dict.js writes the quads in reading direction as the page is displayed (taking /Rotate into account), plus an appearance stream along the text and /OPS_TextDir. It reuses feat(annotations): Caret and Replace annotations in load, save and drawing (#508, part 1) #530's geometry: new quadUnderline and quadSquiggle in js/annotations/corrections/geometry.js, and buildMarkupAppearance in correction-dicts.js (strike midline, underline, squiggle with round joins, highlight as one fill with a multiply blend). /C, /CA, /T, /Contents, /M, /F, popups, /IRT replies and status replies are kept.
• New js/text/leesrichting.js: markups made on vertical or upside-down text take their reading direction from the selected text.
• Markups from other programs that the user did not change keep their quads exactly; files saved by older versions with the old order are repaired on /Rotate 90 and 270. On /Rotate 180 the old order cannot be told apart from upside-down text, so it stays as it was before.
• The line width of underline, strikeout and squiggly is stored (/OPS_LineWidth) and read back; a replacement strike's appearance uses the caret's colour, matching /C.

Verification

• New and adapted tests in geometry.test.mjs, text-markup-dict.test.mjs, leesrichting.test.mjs (real PDFs through pdf.js on every rotation), bestaande-markeringen.test.mjs (old-order files load to the same model; the earlier byte-for-byte guarantee is replaced on purpose), correction-roundtrip.test.mjs, correction-load.test.mjs and correction-wiring.test.mjs. Each failed first for the reported reason.
• Render check of a four-page test file (/Rotate 0/90/180/270) in PDFium and MuPDF: underline, strikeout and squiggle run along the text and highlights cover it, for markups made in the app, markups from another program and repaired old-order markups. The old files show exactly the cross marks of the issue.
• An adversarial review found four defects (no reading direction for vertical text, foreign markups rewritten across the text, replace strike colour, line width lost on reload); all fixed test-first.
• npm run test:unit 2761 passed, 0 failed; npx vite build and npm run typecheck green.

Known, left alone

• On screen the app draws an underline on vertical text horizontally and does not draw a squiggle at all (rendering.js does not use the text direction); the saved appearance is right. Separate follow-up.
• The text-edit strike of feat(annotations): Caret and Replace annotations in load, save and drawing (#508, part 1) #530 does not store its line width yet.

🤖 Generated with Claude Code