feat: add commands for configurable workspace artifacts

[jacebenson]

Closes #34

Changes

• Add workspace command group under Development category
• workspace create --name <name> creates a sys_ux_app_config record
• workspace add-page --name <title> creates a sys_ux_page record
• workspace add-screen --workspace <id> --name <name> [--macroponent <id>] creates a sys_ux_screen record linked to a workspace
• workspace add-macroponent --name <name> creates a sys_ux_macroponent record
• Resolves workspace references by sys_id or name for screen creation
• Uses correct field names per table schema (title for pages, name for screens/macroponents)

Usage

# Create workspace
jsn workspace create --name "My Agent Workspace"

# Add artifacts
jsn workspace add-page --name "home"
jsn workspace add-macroponent --name "home-component"
jsn workspace add-screen --workspace <sys_id> --name "home" --macroponent <sys_id>