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).

workplans/ESRC-WP-0003-metadata-enrichment.md

@@ -4,14 +4,15 @@ type: workplan
 title: "Document metadata enrichment beyond pass-through options"
 domain: infotech
 repo: evidence-source
-status: proposed
+status: finished
 owner: codex
 topic_slug: citation_evidence_mvp
 created: "2026-07-08"
-updated: "2026-07-08"
+updated: "2026-07-09"
 spec_refs:
   - README.md
   - src/pdf/ingest.ts
+  - src/pdf/metadata.ts
 state_hub_workstream_id: "831267a1-fc93-4872-a25b-73793d9c5df4"
 ---
 
@@ -26,7 +27,7 @@ it into the `Document` record without breaking the pure-over-bytes contract.
 
 ```task
 id: ESRC-WP-0003-T01
-status: todo
+status: done
 priority: low
 state_hub_task_id: "45eeef15-41a9-4abd-9436-ed77e2c6b3a4"
 ```
@@ -35,7 +36,7 @@ precedence vs. caller-supplied options (caller wins).
 
 ```task
 id: ESRC-WP-0003-T02
-status: todo
+status: done
 priority: low
 state_hub_task_id: "41ca090f-c709-420a-b7c5-8332e4e82bd1"
 ```
@@ -44,9 +45,9 @@ minimal-metadata PDFs still ingest cleanly.
 
 ```task
 id: ESRC-WP-0003-T03
-status: todo
+status: done
 priority: low
 state_hub_task_id: "0004881b-6577-4a62-a2ff-cbb5c4706b1b"
 ```
 Contract tests over the fixture corpus asserting extracted vs. overridden
-metadata precedence.
+metadata precedence.