[Feature]: Render the pi Notify tool as inline cards

[shrimpwtf]

Summary

Render the pi Notify tool as an inline card in the thread, instead of plain text or nothing.

Tool payload

{ "message": "string", "notifyType": "string" }

• message: the text to show.
• notifyType: the kind of notification, so the card can be styled or grouped by type.

Why

Notify is meant for short, informational events that happen around the agent's work and don't need a reply. Examples:

• a tool rewrite alert from rtk (a command was rewritten before it ran)
• tokens-per-second (TPS) stats
• cache stats

These read best as small cards inline in the timeline, next to the turn they belong to. They shouldn't interrupt the conversation or look like assistant messages.

Proposal

• Accept the Notify tool call from pi sessions and show it as an inline card with the message text.
• Vary the card style by notifyType (for example info, warning, stats), with a sensible default for unknown types.
• Keep it passive: no approval prompt, no effect on thread status.

Open questions

• Which notifyType values should be styled specially, and what should unknown ones look like?
• Should consecutive cards of the same type collapse into one?