Add authorized file-root sync

docs/roadmap.md

@@ -510,7 +510,15 @@ and future group key evolution.
   - `[x]` Scan detects create/update/delete/rename changes.
   - `[x]` Scan output documents that geth never overwrites file roots without a
     recorded future sync decision.
-  - `[ ]` File roots can be synced across nodes.
+  - `[x]` `geth cas root sync <node-id> <name>` pulls authorized remote
+    file-root tree metadata over the protected Iroh control path.
+  - `[x]` Remote file-root sync requires `cas.fetch` on
+    `resource:cas-tree:<name>`.
+  - `[x]` Sync imports CAS tree bytes and records a peer-qualified remote root
+    with path `remote:<node>:<name>` without writing files into the working tree
+    or overwriting same-named local roots.
+  - `[ ]` Future completion applies file-root sync safely with conflict
+    detection and explicit resolution.
 
 - `[~]` Conflict handling.
   Acceptance criteria: