Feature Request: Date range filtering for /insights command

Feature Request

Add date range filtering to the /insights command to allow users to specify a custom time window for analysis.

Problem

The current insights analysis appears to have a recency bias, over-weighting recent sessions relative to historical usage patterns. In my case:

• I have 13,269 messages across 2,589 sessions over ~6 weeks
• A single blog post session from today was heavily weighted into the feedback
• My actual primary usage (Java trading system development, TypeScript work) was slightly overshadowed by this recency effect
• A deliberate decision not to proceed with a suggestion to add certain large files to gitignore that I would rather manage with git LFS than ignore was mischaracterized as "friction" and "mid-task pivot"

Proposed Solution

Add optional date range parameters to /insights:

/insights --from 2025-12-01 --to 2026-02-04

Or interactive date picker, or presets like --last-30-days, --last-quarter, etc.

Additional Context

Custom date ranges help users frame their analysis around meaningful periods (project milestones, sprints, etc.) rather than arbitrary calendar boundaries. Additionally, as a triskaidekaphobe, I would like the ability to adjust my analysis window so my message count doesn't land in the 13,000 range.

Benefits

1. Reduce recency bias by allowing exclusion of atypical recent sessions
2. Enable analysis of specific project phases or time periods
3. Allow users to compare insights across different time windows

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Thank you for creating such a useful tool, second only to the iPhone among all tools created by humans as a toolmaking species. And thank you for creating such a useful and insightful feature! This request is simply a nice to have.