fix(parser): real PDF OCR receives Buffer rejected by PDF.js

[thewrz]

This was written agentically; verify its assertions:

The optional real-OCR integration test cannot recover PART 1 from an image-only PDF. The renderer passes a Node Buffer into unpdf/PDF.js, which rejects it with Please provide binary data as Uint8Array, rather than Buffer. The parser catches this and returns pdf-ocr-unusable, leaving no recovered PART heading.

Evidence

Discovered while validating dependency PR #681. The same focused test fails on the pre-update main checkout at 660cb7347ac7bcea06dc4c10bee6ad824d8c854a (canvas 1.0.8, Zod 4.5.4) and PR head 55e075c45171fa906416e20af22de8b047c09961 (canvas 1.0.9, Zod 4.6.2). Both use pdfjs-dist 6.3.289 / unpdf 1.8.1. This is not a regression introduced by #681. Direct calls to recognizePdfPages expose the same nested cause on both dependency sets. Native canvas 1.0.9 font rendering and PNG encode/decode pass independently.

Run against a migrated and seeded disposable PostgreSQL database:

NODE_ENV=test SPECR_OCR_E2E=1 pnpm exec vitest run --project integration src/parser/pdf/ocr.integration.test.ts

Set DATABASE_URL to that test database. Failure: src/parser/pdf/ocr.integration.test.ts:107, the recovered first PART text is undefined.

Root cause

src/parser/pdf/ocr.ts function pdfData returns the input Buffer unchanged, despite its Uint8Array return type. defaultRenderPageAsImage forwards it through unpdf.renderPageAsImage to PDF.js getDocument; PDF.js explicitly rejects Buffer objects. The existing text extractor instead supplies owned ArrayBuffer data.

Acceptance criteria

• Supply supported binary data at the real OCR rendering boundary while preserving caller ownership.
• Pin this failure with a regression test that runs in normal CI, in addition to the opt-in real OCR test.
• The real image-only PDF test recovers GENERAL and reports pdf-ocr-applied.
• Preserve error redaction and existing OCR timeouts/offline behavior.

Priority: medium; area: PDF parser/OCR. Tracked separately from dependency maintenance.

🤖 Co-authored by Codex.