Support atomic directory promotion across platforms

docs/operations.md

@@ -118,6 +118,12 @@ The directory is immutable once promoted. Configured lanes become
 the bundle and `index.json` are retained for audit and resume validation but
 are not selectable or published implicitly.
 
+Atomic Notarius bundle promotion is supported on Linux, macOS, and Windows.
+On other operating systems, extraction fails before copying the bundle into a
+temporary promotion tree because Narratio has no verified atomic no-replace
+directory primitive there. This is an extraction limitation, not a broader
+platform-support guarantee for every Narratio workflow.
+
 Run-local diagnostics are:
 
 - `runs/{run_id}/extract/notarius.receipt.json`