refactor: replace @react-pdf/pdfkit fork with upstream pdfkit

[diegomura]

Deletes the @react-pdf/pdfkit fork (97 files, ~12k lines) and points renderer and font at upstream pdfkit, pinned to exactly 0.20.1 since render relies on pdfkit internals. Upstream v0.20.0/v0.20.1 landed the last two prerequisites: doc.font() accepts pre-parsed fontkit Font instances, and Node ESM imports resolve to a real Node build (native fs/zlib, self-registering standard fonts), so the BROWSER-gated registerStdFonts in @react-pdf/font stays as-is — rollup treeshakes the standard-font imports out of the server bundle (verified in built output). Also removes the fork from vitest/eslint config and updates CLAUDE.md. Full suite green (224 files / 2454 tests incl. visual snapshots), lint clean; the 9 pre-existing render typecheck errors in addBookmarks.ts are unrelated (reproduce without pdfkit installed).

Closes #2613

Fallout for open PRs:

• Obsoletes refactor(pdfkit): align reference.js with upstream and switch Buffer polyfill to node-stdlib-browser #3409 (fork↔upstream reference.js alignment — the fork is gone) and fix(pdfkit): add pako as a direct dependency #3134 (pako dependency for the fork)
• Supersedes Dm/drop node dependencies #3397 (the upstream-PR staging plan — everything in it landed in upstream 0.20.x)
• Supersedes fix(pdfkit): encrypt strings inside name trees #3508 — its name-tree encryption fix is already in upstream 0.20.1 line-for-line, so the bug it fixes ships with this PR
• Partially obsoletes fix: clamp extreme number values to valid PDF range #3337 — its packages/pdfkit/object.js clamp now belongs in foliojs/pdfkit (the throw still exists upstream); the render/renderGlyphs.ts half still applies here (see unsupported number: …e+21 on long documents with a fixed page-number element, lineHeight is multiplied by fontSize on every pagination pass #3452)
  🤖 Generated with Claude Code

[changeset-bot]

🦋 Changeset detected

Latest commit: c0b5727

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 11 packages

Name	Type
@react-pdf/renderer	Minor
@react-pdf/font	Minor
@react-pdf/math	Major
@react-pdf/mermaid	Major
next-14	Patch
next-15	Patch
@react-pdf/vite-example	Patch
@react-pdf/types	Patch
@react-pdf/layout	Patch
@react-pdf/render	Patch
@react-pdf/stylesheet	Patch

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