feat(pdf): extract standalone PDF ingest package (ESRC-WP-0001)

Bootstrap evidence-source from the citation-evidence src/source PDF slice.

- Headless core (src/pdf): ingest/extract/fingerprint, importing domain
  contracts from @citation-evidence/engine/shared (no local copies)
- Browser upload helpers isolated under src/browser behind a ./browser
  entry point, with an eslint boundary keeping the core browser-free
- pnpm/TS/vitest/eslint scaffold; 52 tests (contract + determinism)
- Fixtures resolved from the sibling citation-evidence checkout, not
  duplicated (real PII) — see docs/ADR-0002; suites skip when absent
- Boundary + fixture decisions recorded as docs/ADR-0001 / ADR-0002
- README/SCOPE rewritten; capability.infotech.pdf-evidence-ingest
  registered, NO_CAPABILITIES removed
- Follow-on workplans ESRC-WP-0002..0004 queued; ESRC-WP-0001 finished

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

package.json

@@ -0,0 +1,43 @@
+{
+  "name": "@citation-evidence/evidence-source",
+  "version": "0.1.0",
+  "private": true,
+  "description": "Headless document ingest, fingerprinting, and canonical-text extraction for the citation-evidence ecosystem. PDF slice.",
+  "license": "Apache-2.0",
+  "type": "module",
+  "packageManager": "pnpm@9.15.0",
+  "engines": {
+    "node": ">=20.10.0"
+  },
+  "files": [
+    "src",
+    "docs",
+    "README.md",
+    "LICENSE"
+  ],
+  "exports": {
+    ".": "./src/index.ts",
+    "./browser": "./src/browser/index.ts"
+  },
+  "scripts": {
+    "test": "vitest run",
+    "test:watch": "vitest",
+    "lint": "eslint .",
+    "typecheck": "tsc --noEmit"
+  },
+  "dependencies": {
+    "@citation-evidence/engine": "link:../citation-engine",
+    "pdfjs-dist": "^4.4.168"
+  },
+  "devDependencies": {
+    "@eslint/js": "^9.7.0",
+    "@types/node": "^20.14.0",
+    "eslint": "^9.7.0",
+    "eslint-import-resolver-typescript": "^3.6.3",
+    "eslint-plugin-import": "^2.30.0",
+    "globals": "^15.9.0",
+    "typescript": "^5.5.4",
+    "typescript-eslint": "^8.0.0",
+    "vitest": "^2.0.5"
+  }
+}