feat: Add Feishu interactive card delivery

[yaosiyuuu6]

What changed

This PR adds a Feishu-friendly reading path for Follow Builders digests by supporting interactive card delivery in addition to the existing plain text / Telegram / email flow.

Why

For Feishu users, plain text and markdown-post delivery collapse spacing too aggressively. That makes digest sections and builder blocks harder to scan on mobile. Interactive cards preserve hierarchy better:

• section headings stay bold
• item titles stay bold
• item blocks are separated with dividers instead of relying on empty lines
• the layout survives Feishu rendering more reliably

Implementation

• add scripts/format-chat-digest.js to normalize digest text into a stable chat-friendly structure
• add scripts/render-feishu-card.js to convert the final digest text into Feishu interactive card JSON
• update the skill delivery workflow so stdout delivery can optionally route through direct Feishu card sending when the config includes:
  • delivery.channel = "feishu"
  • delivery.target = "<open_id or chat_id>"
  • delivery.format = "interactive_card"
• document the new config shape and Feishu card behavior in both English and Chinese READMEs
• extend config/config-schema.json with the Feishu card delivery fields
• update the digest prompt and sample output so the generated digest structure is easier to transform into a card reliably

User impact

OpenClaw + Feishu users can choose a card-based morning digest that is easier to read on mobile. Existing users who stay on plain text / Telegram / email are unaffected.

Validation

• validated the formatter and card renderer locally with:
  • node scripts/format-chat-digest.js --file examples/sample-digest.md | node scripts/render-feishu-card.js
• sent live Feishu test messages to compare:
  • markdown post
  • exact post JSON
  • interactive card
• confirmed the interactive card presentation was the preferred result for the target reading workflow