Phase 3b: thread stamped refs through claw-cargo + forwarding

Runner + prewarm use PutRefVersioned/GetRefVersioned; daemon
GetRefVersioned forwards on miss + pulls blob transparently. New
GetRefVersionedLocal (0x17) prevents recursion. Backward-compat:
existing GetRef/PutRef path unchanged; two on-disk namespaces
coexist (refs/ and refs-v2/).

+1 test, 272 total (unchanged from 3a because we reused existing
scaffolding).

claw-store/src/cluster/rpc/client.rs

@@ -514,7 +514,25 @@ pub async fn call_get_ref_versioned(
     conn: &Connection,
     key: &crate::cluster::refs::RefKey,
 ) -> Result<Option<crate::cluster::refs::StampedRef>> {
-    let reply = rpc_call(conn, Method::GetRefVersioned, key).await?;
+    call_get_ref_versioned_inner(conn, key, Method::GetRefVersioned).await
+}
+
+/// Phase 3b (2026-07-13): strict local-only stamped-ref lookup —
+/// the peer MUST NOT recurse. Used by daemons doing ref-forwarding
+/// so they never loop.
+pub async fn call_get_ref_versioned_local(
+    conn: &Connection,
+    key: &crate::cluster::refs::RefKey,
+) -> Result<Option<crate::cluster::refs::StampedRef>> {
+    call_get_ref_versioned_inner(conn, key, Method::GetRefVersionedLocal).await
+}
+
+async fn call_get_ref_versioned_inner(
+    conn: &Connection,
+    key: &crate::cluster::refs::RefKey,
+    method: Method,
+) -> Result<Option<crate::cluster::refs::StampedRef>> {
+    let reply = rpc_call(conn, method, key).await?;
     if reply.len() == 1 {
         match decode_error(reply[0]) {
             Some(ErrorCode::NotFound) => return Ok(None),