/insights should support a configurable time range

Feature Request

The /insights command currently doesn't accept any arguments to control the time range of the analysis. It would be useful to support flags like:

• --days 30 — analyze the last 30 days
• --from 2026-02-01 --to 2026-03-01 — analyze a specific date range

Current behavior

Running /insights analyzes a fixed window (appears to default to ~7 days of deep analysis). There's no way to expand or narrow the range.

Expected behavior

/insights 30d or /insights --days 30 should let users control how far back the analysis goes.

Why this matters

Users who want a monthly retrospective or a broader view of their workflow patterns can't get one without re-running insights multiple times. A configurable range would make the report much more actionable for longer-term workflow improvements.