feat(storage): add registerStorageCommand for mosaic storage CLI surface

Implements CU-05-02: adds `mosaic storage` command group with subcommands
status, tier show, tier switch, export, import, and migrate. Pragmatic
stubs print actionable instructions for unimplemented export/import tiers.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

pnpm-lock.yaml

@@ -478,6 +478,9 @@ importers:
       '@mosaicstack/queue':
         specifier: workspace:*
         version: link:../queue
+      '@mosaicstack/storage':
+        specifier: workspace:*
+        version: link:../storage
       '@mosaicstack/types':
         specifier: workspace:*
         version: link:../types
@@ -599,6 +602,9 @@ importers:
       '@mosaicstack/types':
         specifier: workspace:*
         version: link:../types
+      commander:
+        specifier: ^13.0.0
+        version: 13.1.0
     devDependencies:
       typescript:
         specifier: ^5.8.0