Add safe file-root apply

docs/roadmap.md

@@ -519,8 +519,12 @@ and future group key evolution.
     or overwriting same-named local roots.
   - `[x]` Background live-sync imports updated authorized file-root trees from
     sync-status `cas-tree:<name>` watermarks and stores per-peer cursors.
-  - `[ ]` Future completion applies file-root sync safely with conflict
-    detection and explicit resolution.
+  - `[x]` `geth cas root apply <root> --to <path>` materializes missing files
+    and directories from a CAS tree without deleting extras or overwriting local
+    edits.
+  - `[x]` Apply records durable conflicts for differing local paths.
+  - `[ ]` Future completion adds a richer three-way apply using base/local/remote
+    trees for automatic safe updates and deletes.
 
 - `[~]` Conflict handling.
   Acceptance criteria: