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>

packages/storage/package.json

@@ -23,7 +23,8 @@
   "dependencies": {
     "@electric-sql/pglite": "^0.2.17",
     "@mosaicstack/db": "workspace:^",
-    "@mosaicstack/types": "workspace:*"
+    "@mosaicstack/types": "workspace:*",
+    "commander": "^13.0.0"
   },
   "devDependencies": {
     "typescript": "^5.8.0",