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>

registry/indexes/capabilities.yaml

@@ -1,4 +1,22 @@
 version: 1
-updated: '2026-06-16'
-domain: helix_forge
-capabilities: []
+updated: '2026-07-08'
+domain: infotech
+capabilities:
+- id: capability.infotech.pdf-evidence-ingest
+  name: Headless PDF Evidence Ingest
+  summary: Turns raw PDF bytes into an engine-shaped Document + DocumentRepresentation
+    — SHA-256 fingerprint, canonical text, page map, and gap-free offset map — as a
+    runtime-agnostic library with no viewer, persistence, or React coupling.
+  vector: D2 / A1 / C1 / R1
+  domain: infotech
+  status: draft
+  owner: evidence-source
+  path: registry/capabilities/capability.infotech.pdf-evidence-ingest.md
+  tags:
+  - pdf
+  - ingest
+  - fingerprint
+  - canonical-text
+  - evidence
+  consumption_modes:
+  - library import