feat(pipeline): add PDF as a first-class InDesign input

[PAMulligan]

Summary

Makes PDF a first-class input to the InDesign-to-React pipeline (#64, part of #62). InDesign-exported PDFs are what designers actually hand engineering, so the parser ingests them into the same IR the IDML parser emits — keeping the token mapper (#65) and the upcoming component generator (#66) source-agnostic.

New packages/pipeline/src/pdf/ subsystem (via pdfjs-dist) plus a source-agnostic parseSourceFile entry and CLI integration.

What it does

• Text — extracts positioned glyph runs and clusters them: runs → lines (split on large gaps so columns don't merge) → columns → text frames.
• Styles — infers a heading/body/caption scale from font-size buckets, synthesized as ParagraphStyles the mapper clusters exactly as IDML styles.
• Color — derives a swatch palette from operator-list fills/strokes and dominant image colors (CMYK/RGB/Gray → sRGB), de-duplicated within tolerance.
• Images — extracts embedded image XObjects, decodes to PNG (pngjs), and writes them to an --assets dir, addressable from the IR.
• Geometry — flips PDF's bottom-left origin to the IR's top-left pixel space at a configurable DPI.
• Fidelity — emits TEXT_FROM_GLYPHS, NO_EMBEDDED_FONTS, VECTOR_ONLY_PAGE, MULTI_COLUMN_DETECTED, IMAGE_NOT_EXTRACTED warnings, surfaced by the CLI and documented in docs/pipeline/indesign-pdf-fidelity.md.

CLI & API

# Auto-detects .pdf vs .idml; --source-priority forces a path.
aurelius-indesign brochure.pdf --emit-tokens ./src/tokens --assets ./public/assets

import { parsePdfFile } from "@aurelius/pipeline/pdf";
import { parseSourceFile } from "@aurelius/pipeline";
const { document } = await parseSourceFile("brochure.pdf", { sourcePriority: "pdf", assetDir: "public/assets" });

runCli is now async; meta.source ("idml" | "pdf") was added to the IR.

Acceptance criteria (#64)

• Fixture PDF → valid IR consumable by the mapper without a companion IDML (PDF → IR → tokens tested)
• CLI accepts .pdf as a primary input and runs PDF → IR → tokens end-to-end
• Parity test: same-shape IDML & PDF agree on page count and heading/body buckets within tolerance
• Embedded images extracted and addressable from the IR
• Swatch palette derived from the PDF when no IDML is supplied
• Fidelity warnings in CLI output + documented in docs/pipeline/indesign-pdf-fidelity.md
• README + pipeline docs describe PDF as first-class with a "designer hands you a PDF" quickstart
• Unit tests cover text-heavy, image-heavy, multi-column, single-page brochure, and vector-only/outlined PDFs

Testing

• pnpm --filter @aurelius/pipeline typecheck / test / build ✅ — 117 tests (24 new)
• Repo-wide eslint . (0 errors) and prettier --check . ✅; check-doc-counts ✅; lockfile in sync (pnpm 9 compatible)
• Verified the compiled CLI on a real PDF: PDF IR report, PDF → tokens, and image extraction (image-1.png) all work; config/font-map.json resolves from dist/

Notes

• Not pixel-perfect by design — the goal is a usable, styled IR for the generator with manual touch-ups. IDML remains preferred when available (richer style metadata); force PDF with --source-priority pdf to verify parity.
• pdfjs-dist runs in Node with no worker/canvas (data-extraction only). New deps: pdfjs-dist, pngjs (runtime), pdf-lib, @types/pngjs (dev, fixtures).

Closes #64
Part of #62

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