feat: AI-generated session summary on hover

[matoushavlena]

Summary

Priority: P0 | Category: Context Preservation

Show an AI-generated context snapshot when hovering over a session — eliminating the re-orientation cost of switching between multiplexed agents.

Problem

When you return to a session after being away, you don't remember where it is. You open it and scroll up through logs. You re-read tool calls. You try to reconstruct what the agent was doing and where it got to. This re-orientation cost is the core tax of multiplexing.

Even deciding whether to open a session requires context you don't have. You see a session name and a status color, but you don't know what it's actually working on right now.

Proposed Solution

When you hover over a session, show a tooltip or popover with a 2-3 line AI-generated summary of:

1. What the agent is currently doing: "Refactoring the auth middleware to use JWT validation"
2. Where it is in the process: "3 of 5 files updated, currently working on middleware/auth.ts"
3. What it needs (if anything): "Waiting for approval to delete legacy session handler"

The summary should be generated from the agent's recent conversation context, compressed into a glanceable snapshot. It should update as the agent progresses.

Acceptance Criteria

• Hovering over any session shows a context summary without opening the session
• Summary is concise (2-3 lines max) and reflects current agent state
• Summary updates as the agent makes progress
• Latency is low enough to feel instant (pre-compute summaries, don't generate on hover)
• Summary includes what the agent needs from the user, if anything

Open Questions

• Generate summaries locally or via API call? (Latency vs. quality tradeoff)
• How often to refresh summaries? On every agent message? Every N seconds?
• Should the summary be clickable to expand into a fuller recap?