[codex] ROY-36: Add hello command to CLI

[zhangweijian97]

Linear issue: ROY-36

This PR was created by the Agent-Driven Development Hub (ADHD.ai) workflow.

Includes:

• plan + implement session output
• separate review/testing session

[zhangweijian97]

ADHD.ai review for ROY-36

Result: PASS

Token usage: input 5827, output 1189, total 7016

The PR adds a simple hello command with optional --name flag. All 130 tests pass, code follows existing patterns, type safety is maintained, and the help documentation is updated. Manual testing confirms the command works correctly in both modes (with and without name).

No bugs found.