Use merged AI agent workflow and Handbook

[ocots]

Summary

• Point AIHello.yml at the merged main branch of CTActions.
• Use the merged main branch of Handbook for the hello agent.
• Keep the manual workflow inputs and organization secrets unchanged.

Related PR

• CTActions DeepSeek model fix: Fix DeepSeek model identifier for Albert CTActions#73

The previous run confirmed that the cross-repository checkout and secrets worked, but Albert returned HTTP 404 for the model identifier. The CTActions fix changes the deepseek alias to Albert's deepseek-v4-flash identifier.

Test plan

• Validate the workflow as YAML.
• Run git diff --check.
• Merge the CTActions fix.
• Run AI Hello manually from the Actions UI.