feat: Thread timeline visualization with Gantt chart

[rlaope]

Problem

The current dashboard shows metrics and event logs, but lacks visual representation of thread lifecycles:

• Hard to understand thread execution patterns
• Cannot see thread concurrency visually
• Difficult to identify long-running threads

Proposed Solution

Implement a Gantt chart style timeline visualization:

1. Horizontal bars representing thread lifecycles
2. Color coding by thread state (running, pinned, ended)
3. Zoomable and scrollable timeline
4. Click to view thread details

Acceptance Criteria

• Add timeline section to dashboard
• Display threads as horizontal bars (START to END)
• Color code: green (running), red (pinned), gray (ended)
• Implement zoom (1s, 10s, 1min, 5min views)
• Add horizontal scroll for time navigation
• Click bar to open thread detail modal
• Show carrier thread assignment on hover

Technical Considerations

• Use Canvas or SVG for rendering (consider performance with 1000+ threads)
• Virtual scrolling for large thread counts
• Aggregate threads when zoomed out (show density)
• Consider using PixiJS for WebGL acceleration

UI Mockup

Timeline                              [1s] [10s] [1min] [5min]
├─────────────────────────────────────────────────────────────┤
│ 00:00:00    00:00:05    00:00:10    00:00:15    00:00:20    │
├─────────────────────────────────────────────────────────────┤
│ VT-1  ████████████████░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░  │
│ VT-2  ░░░░████████████████████████████████████████░░░░░░░  │
│ VT-3  ░░░░░░░░░░░░████████████████░░░░░░░░░░░░░░░░░░░░░░░  │
│ VT-4  ░░░░░░░░░░░░░░░░░░░░████████████████████████████████  │
│ VT-5  ████████░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░░  │
└─────────────────────────────────────────────────────────────┘

Legend: ████ Running   ████ Pinned   ░░░░ Not started/Ended

Data Structure

{
  "threads": [
    {
      "threadId": 123,
      "threadName": "VT-1",
      "startTime": 1704067200000,
      "endTime": 1704067205000,
      "pinnedRanges": [
        { "from": 1704067202000, "to": 1704067203000 }
      ]
    }
  ]
}