Run history trends: sparklines, streaks, averages

[CKGrafico]

Problem

Run history is a flat table of runs with timestamps, durations, and exit codes. No trends, no insights, no visual summary of how a loop is performing over time.

Solution

Add visual trend indicators to the run history panel.

Features

1. Sparkline of durations

   • Unicode block characters: low blocks for fast, tall for slow
   • Shows last N runs (up to 20, fits in panel width)
   • Color: green if under average, red if over average
   • Example: fast loop -> slow loop -> back to fast
     ▁▂▁▂▃█▆▄▂▁

2. Success/failure streak

   • "Streak: 5 successes" or "Streak: 3 failures"
   • Color-coded: green for success streak, red for failure streak
   • Helps spot degrading loops

3. Average duration

   • "Avg: 1.2s" next to the sparkline
   • Computed from last N runs (same window as sparkline)

4. Last failure timestamp

   • "Last failure: 2h ago" if any recent failure exists
   • Helps answer "when did this last break?"

5. Trend arrow

   • Up arrow if getting slower (recent avg > overall avg)
   • Down arrow if getting faster
   • Dash if stable

Layout

+----------------------------------------------+
| Run History |
| |
| Durations: ▁▂▁▂▃█▆▄▂▁ Avg: 1.2s Trend: ▲ |
| Streak: 5 successes Last failure: 2h ago |
| |
| 14:32:10 ✓ 1.2s 145B |
| 14:30:10 ✓ 1.1s 33B |
| 14:28:10 ✗ 0.1s 0B |
| ... |
+----------------------------------------------+

Implementation

• Pure computation from existing runHistory data (no new storage)
• Sparkline rendered with Unicode block characters (no external dependency)
• Recent N = Math.min(runHistory.length, panelWidth / 2)
• Colors from theme.ts

Acceptance criteria

• Sparkline of last N run durations
• Color: green under avg, red over avg
• Success/failure streak counter
• Average duration display
• Last failure timestamp (relative: "2h ago")
• Trend arrow (up = slower, down = faster, dash = stable)
• All computed from existing runHistory (no new storage)

Part of v2.0.0 epic #4

[CKGrafico]

Run history trends implemented: sparkline, success/failure streaks, average duration, last failure timestamp. Closed.