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/mosaic/package.json

@@ -32,6 +32,7 @@
     "@mosaicstack/macp": "workspace:*",
     "@mosaicstack/prdy": "workspace:*",
     "@mosaicstack/quality-rails": "workspace:*",
+    "@mosaicstack/storage": "workspace:*",
     "@mosaicstack/types": "workspace:*",
     "@clack/prompts": "^0.9.1",
     "commander": "^13.0.0",

packages/mosaic/src/cli.ts

@@ -3,6 +3,7 @@
 import { createRequire } from 'module';
 import { Command } from 'commander';
 import { registerQualityRails } from '@mosaicstack/quality-rails';
+import { registerStorageCommand } from '@mosaicstack/storage';
 import { registerAgentCommand } from './commands/agent.js';
 import { registerMissionCommand } from './commands/mission.js';
 // prdy is registered via launch.ts
@@ -318,6 +319,10 @@ registerMissionCommand(program);
 
 registerQualityRails(program);
 
+// ─── storage ─────────────────────────────────────────────────────────────
+
+registerStorageCommand(program);
+
 // ─── update ─────────────────────────────────────────────────────────────
 
 program