- Add main_content.rml for sandbox-test app with test cards for Timer, JSON, Crypto, Storage
- Add sandbox test functions to shell.lua (testSandboxTimer, testSandboxJSON, etc.)
- Register sandbox-test in builtin_ids and shellNavigateTo paths
- Add sandbox-test styles to shell.rml
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
