Add Feishu Channel

This skill adds Feishu (飞书) support to NanoClaw using the skills engine for deterministic code changes, then walks through interactive setup.

Phase 1: Pre-flight

Check if already applied

Read .nanoclaw/state.yaml. If feishu is in applied_skills, skip to Phase 3 (Setup). The code changes are already in place.

Ask the user

Use AskUserQuestion to collect configuration:

AskUserQuestion: Do you have a Feishu app already, or do you need to create one?

If they have one, collect FEISHU_APP_ID and FEISHU_APP_SECRET now. If not, we'll create one in Phase 3.

Phase 2: Apply Code Changes