Point README at citation-evidence umbrella during MVP phase

Code lives upstream in citation-evidence/src/source/ during the MVP.
README documents that and points at SharedContracts.md for ingest,
fingerprint, and recovery contract changes.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

README.md

@@ -1,3 +1,16 @@
-# repo-seed
+# evidence-source
 
-A git repository template to bootstrap coulomb projects from.
+Document source, ingestion, extraction, metadata, and citation recovery —
+PDF/HTML/MD ingest, fingerprinting, page-/offset-map construction,
+canonical-text extraction, and the recovery behavior for stale selectors.
+
+## MVP status: INTENT only
+
+During the citation-evidence MVP, code lives upstream in
+[`citation-evidence`](../citation-evidence/) under `src/source/`. This repo
+currently holds `INTENT.md` describing what will move here. Contract
+changes belong in
+[`citation-evidence/wiki/SharedContracts.md`](../citation-evidence/wiki/SharedContracts.md),
+not here.
+
+Per the dependency map, source depends on `shared/` and `engine/` only.