feat(memory): add registerMemoryCommand for mosaic memory CLI surface

Adds mosaic memory CLI with four subcommands: search, stats,
insights list, and preferences list. Commands accept --db flag
(or MEMORY_DB_URL/DATABASE_URL env) to connect to pgvector or
keyword adapter. Smoke tests verify command wiring without DB.

Task: CU-05-04

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

packages/memory/package.json

@@ -25,6 +25,7 @@
     "@mosaicstack/db": "workspace:*",
     "@mosaicstack/storage": "workspace:*",
     "@mosaicstack/types": "workspace:*",
+    "commander": "^13.0.0",
     "drizzle-orm": "^0.45.1"
   },
   "devDependencies": {