fix: verify complete offline assets before replacing staged runtime

docs/ROADMAP.md

@@ -49,6 +49,9 @@ Status: implementation started; no production release yet. Windows VM tests use
 - [ ] Isolated extraction workers with timeouts and resource ceilings.
 
 ## 5. Release gates
+- [x] Preflight native license and the complete offline Google model pair before
+  modifying staged resources; corrupted/missing assets preserve existing worker.
+- [ ] Atomic resource staging and interrupted-copy recovery for release bundles.
 - [x] Shared monotonic Basic/Debug search metrics, granular bounded engine traces,
   actual worker query diagnostics, and headless JSON performance output.
 - [ ] Verify detailed performance UI interaction on native desktop platforms;