Feature: CUI documentation and usage examples

[smota]

Parent epic: #1

Job to be done

When users discover the CUI, I want clear docs explaining when to use skills cui vs skill-cui and how standalone mode differs.

Scope

• Update README command list and examples.
• Document skills cui core mode.
• Document npx skill-cui standalone mode.
• Document --no-confirmation safety implications.
• Document dependency and capability limits.

Acceptance criteria

• README mentions CUI command and standalone package.
• Docs explain that standalone mode invokes npx skills and parses supported output.
• Docs include examples for list/filter/search/install/update/remove/move flows.