Adds a right-side slide-out sidebar for the current chat/session plan.

• Live-preview Markdown checklist editor with rendered checkbox controls.
• Persists the plan per chat_jid in Piclaw's extension KV store.
• Survives browser refreshes and follows the active web chat/session.
• Provides a plan tool with get and set actions so the model can inspect or update the same session plan.
• Includes a Submit to model button that saves the sidebar content and sends it back into the current session as an agent message.

Tool

{ "action": "get" }

{ "action": "set", "markdown": "- [ ] Verify build\n- [ ] Report back" }

By default the tool uses the active chat/session. Pass chat_jid only when intentionally reading or writing another session.