Implement ESRC-WP-0002/0003/0004: HTML/MD ingest, metadata, recovery

Add ingestHtml and ingestMarkdown with ADR-0003 pageless offset semantics,
PDF intrinsic metadata extraction with caller-wins merge (WP-0003), and
citation recovery primitives including re-ingest reconcile, local quote
search, and pluggable discovery hooks (ADR-0004). Mark all three workplans
finished with contract tests (80 passing).

SCOPE.md

@@ -8,8 +8,8 @@
 
 ## One-liner
 
-Headless PDF ingest that turns document bytes into engine-owned evidence
-contracts (fingerprint, canonical text, page/offset maps).
+Headless document ingest that turns PDF, HTML, and Markdown bytes into
+engine-owned evidence contracts (fingerprint, canonical text, page/offset maps).
 
 ---
 
@@ -18,25 +18,30 @@ contracts (fingerprint, canonical text, page/offset maps).
 The rest of the citation-evidence ecosystem (anchoring, evidence linking,
 binders) needs a stable, runtime-agnostic way to go from *raw document bytes*
 to a `Document` + `DocumentRepresentation`. This repo owns that transformation
-for PDFs — pure over bytes, no persistence, no viewer, no UI framework.
+for PDF, HTML, and Markdown — pure over bytes, no persistence, no viewer,
+no UI framework.
 
 ---
 
 ## In Scope
 
 - PDF byte ingest → `{ document, representation }` (`ingestPdf`)
+- HTML byte ingest → `{ document, representation }` (`ingestHtml`)
+- Markdown byte ingest → `{ document, representation }` (`ingestMarkdown`)
 - PDF text extraction → canonical text + page map + gap-free offset map (`extractPdf`)
+- PDF intrinsic metadata extraction with caller-wins merge (`extractPdfMetadata`)
 - SHA-256 byte fingerprinting (`fingerprintBytes`)
+- Citation recovery primitives: re-ingest/reconcile, local quote search, discovery hooks
 - Browser upload helpers behind a separate entry point (`createPdfByteStore`, `ingestPdfFromFile`)
 
 ---
 
 ## Out of Scope
 
-- HTML / Markdown representations (deferred — see `workplans/`)
 - Persisting documents or representations (caller's job)
 - Viewer URL resolution and blob-vs-fixture policy (stays in `citation-evidence`)
-- Citation recovery / external source discovery (deferred)
+- Stale selector detection and anchor resolution (stays in `evidence-anchor`)
+- Network-backed external source discovery implementations (host registers hooks)
 - Defining domain contracts — those are owned by `citation-engine`
 
 ---
@@ -51,7 +56,7 @@ for PDFs — pure over bytes, no persistence, no viewer, no UI framework.
 
 ## Not Relevant When
 
-- You need HTML/Markdown ingest (not yet implemented)
+- You need formats beyond PDF/HTML/Markdown (not yet implemented)
 - You need viewer/session/UI behavior (see `citation-evidence`)
 - You are changing the `Document`/`DocumentRepresentation` contract (see `citation-engine`)
 
@@ -60,7 +65,7 @@ for PDFs — pure over bytes, no persistence, no viewer, no UI framework.
 ## Current State
 
 - Status: active
-- Implementation: partial (PDF slice implemented; HTML/MD and recovery deferred)
+- Implementation: partial (PDF/HTML/MD ingest, metadata enrichment, recovery primitives)
 - Stability: evolving
 - Usage: internal (consumed by `citation-evidence` across the repo boundary)
 
@@ -92,7 +97,7 @@ for PDFs — pure over bytes, no persistence, no viewer, no UI framework.
 ## Getting Oriented
 
 - Start with: `README.md`, then `docs/ADR-0001-extraction-boundary.md`
-- Key files / directories: `src/pdf/` (headless core), `src/browser/` (upload helpers)
+- Key files / directories: `src/pdf/`, `src/html/`, `src/markdown/`, `src/recovery/`, `src/browser/`
 - Entry points: `src/index.ts` (headless), `src/browser/index.ts` (browser)
 
 ---