Fetch CAS blobs over Iroh

docs/architecture.md

@@ -111,9 +111,16 @@ into CAS tree objects while reporting create/update/delete/rename changes. These
 scans are local metadata only and never overwrite the working tree. The daemon
 also has durable local file-conflict records with explicit resolution choices;
 future cross-node file sync will create those records automatically instead of
-silently applying ambiguous remote changes. Iroh-blobs, providers, encrypted
-blobs, richer cache policies, cross-node file roots, and automatic conflict
-detection are future work.
+silently applying ambiguous remote changes.
+
+As a bootstrap network path, `geth cas fetch <node-id> <hash>` dials an
+imported signed peer card over the daemon-owned Iroh control ALPN. The serving
+daemon validates the caller's peer-card signature and observed Iroh EndpointID,
+then reduces local auth ops and requires `cas.fetch` on `resource:cas:local`
+before returning blob bytes. The requester verifies that the returned bytes hash
+to the requested BLAKE3 CAS hash before storing them. Iroh-blobs, provider
+tracking, encrypted blobs, richer cache policies, cross-node file roots, and
+automatic conflict detection are future work.
 
 `geth-db` currently registers local SQLite paths as DB resources and reports
 local-only sync status plus a read-only SQLite schema summary/hash. It also