Add local CAS pin metadata

AGENTS.md

@@ -116,6 +116,8 @@ Roadmap items should be actionable and checkable:
   enforcement are still roadmap work.
 - The daemon persists local keychain init/admin-key ops and reduces them for
   `keychain status`. SSH signature capture/verification is still roadmap work.
+- Local CAS supports pin/unpin metadata, surfaced through `cas list`. Cache
+  cleanup and eviction policy are still roadmap work.
 - Signed peer-card LAN discovery payloads, peer auth over Iroh, cr-sqlite,
   iroh-docs, iroh-gossip, iroh-blobs, Automerge sync, real auth enforcement,
   OpenSSH KRL generation, and Keyhive/BeeKEM-style authorization are future