Insights report shows impossible session hours (10,800h in 17 days)

Bug Description

The /insights command reports mathematically impossible usage statistics.

Example

• Report claims: 10,830 hours across 3,559 sessions
• Actual time period: 17 days (2026-01-14 to 2026-02-04)
• Maximum possible: 408 hours (17 × 24)

The reported hours would require ~637 hours per day.

Likely Causes

1. Summing overlapping parallel sessions (background agents, multiple terminals) without deduplication
2. Unit conversion error (e.g., seconds displayed as hours)
3. Counting idle "session open" time multiple times across concurrent sessions

Impact

The qualitative analysis appears reasonable, but the raw numbers undermine trust in the report.

Environment

• Claude Code CLI
• macOS Darwin 25.2.0