Track CAS providers

docs/roadmap.md

@@ -248,9 +248,12 @@ authorization and durable-state boundaries clear.
   - `[x]` The requester verifies returned bytes against the requested BLAKE3
     CAS hash before storing them locally.
   - `[x]` Local add/get/hash/has/list behavior remains backward compatible.
+  - `[x]` Successful fetches record the serving peer as a local provider for
+    the CAS hash.
+  - `[x]` `geth cas providers <hash>` lists locally known providers.
+  - `[x]` Tests cover local provider metadata storage.
   - `[ ]` Replace the bootstrap control-ALPN transfer with `iroh-blobs`
     provider/fetch behavior.
-  - `[ ]` Provider tracking is recorded locally.
 
 - `[x]` CAS pin and cache policy.
   Acceptance criteria: