Add a Mission Control swimlane view

[raphant]

Goal

Show concurrent agent work in a time-oriented view that complements the node graph.

Proposed change

Add one swimlane per agent with thinking, tool use, waiting, blocked, idle, and completed intervals.
Keep the swimlane and graph on the same Review mode clock.

Acceptance criteria

• Every visible agent has one labeled lane.
• Intervals use the existing event timestamps and state transitions.
• Selecting an interval highlights the corresponding graph node and transcript range.
• Zoom and seek stay synchronized with Review mode.
• The view remains usable with at least 50 agents and 5,000 events.

Source

• web/components/agent-visualizer/timeline-panel.tsx owns the current timeline panel.
• web/components/agent-visualizer/canvas/detect-state-changes.ts derives visual state transitions.