PI: pi-ai & pi-agent-core

# 1, Why does Openclaw need Pi?  00:00

# 2. Layer-1. Pi-ai：  01:35

    Unify the inputs & outputs of various AI models.

    Context handoff:    03:32

# 3. Layer-2. Pi-agent-core:     06:48

    5-sprint agent loop:    07:21

    Events & event handlers:     11:32

    Abort, Interrupt & followup:    14:16

# 4. Summary and next: 15:13