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>

workplans/ESRC-WP-0002-html-markdown-representations.md

@@ -0,0 +1,55 @@
+---
+id: ESRC-WP-0002
+type: workplan
+title: "HTML and Markdown source representations"
+domain: infotech
+repo: evidence-source
+status: proposed
+owner: codex
+topic_slug: citation_evidence_mvp
+created: "2026-07-08"
+updated: "2026-07-08"
+spec_refs:
+  - README.md
+  - docs/ADR-0001-extraction-boundary.md
+  - ../citation-engine/src/shared/document.ts
+---
+
+# ESRC-WP-0002 — HTML and Markdown source representations
+
+The PDF slice (ESRC-WP-0001) established the ingest boundary and contract shape.
+This workplan extends ingest to HTML and Markdown sources, producing the same
+`{ document, representation }` pair over engine-owned contracts.
+
+## Open questions
+
+- Which `representationType` values do HTML/MD map to, and do they need new
+  `DocumentRepresentation` fields in `citation-engine`?
+- How is canonical text + offset map derived for reflowable formats that have
+  no fixed pages? (Page map may be empty or synthetic.)
+
+## Sketch
+
+```task
+id: ESRC-WP-0002-T01
+status: todo
+priority: medium
+```
+Define the HTML/MD representation contract with `citation-engine`; agree
+`representationType` and any offset/page semantics for pageless formats.
+
+```task
+id: ESRC-WP-0002-T02
+status: todo
+priority: medium
+```
+Implement `ingestHtml` / `ingestMarkdown` in `src/html/` and `src/markdown/`,
+reusing `fingerprintBytes` and the canonical-text normalizer.
+
+```task
+id: ESRC-WP-0002-T03
+status: todo
+priority: medium
+```
+Add fixture-driven contract tests mirroring the PDF suite; decide fixture
+ownership per ADR-0002.