Feature: Weekly email digest of time tracking insights

[gloomcheng]

Problem

As a busy developer, I don't always remember to run `toki insights` or `toki report`. I'd like a passive way to receive my productivity summary.

Current State

All reporting is pull-based (user must run commands).

Proposed Solution

1. Scheduled digest - Weekly email with insights summary
2. Configurable delivery - Email, Slack DM, or local notification
3. Highlights focus - Only show interesting patterns, not raw data

Example Email

```
📊 Your Week in Review (Dec 30 - Jan 5)

Total: 42h 15m
Top Project: hygieia (28h)
Peak Productivity: Tue 2pm-5pm
Focus Score: 78% (↑ from last week)

⚠️ Noticed: 3 issues exceeded estimates
💡 Tip: Your focus drops after 4pm - consider shorter afternoon blocks
```

Related Pain Points

• Forgetting to check insights
• Want passive, actionable feedback