Feature Request: Per-project filtering for /insights command

Problem

The /insights command aggregates data across all projects, producing misleading reports for users who work across multiple projects. In my case, it conflated a Scala project with a Ruby/Rails project, incorrectly attributing Ruby-specific patterns and file references to the wrong codebase.

Requested Features

1. Per-project filtering: Allow /insights to filter to the current project directory (e.g. /insights --project or auto-filter by cwd)
2. Data reset: Allow users to clear insights history to start fresh (e.g. /insights --reset)
3. Project tagging in facets: Store the project path in facet JSON files so data can be filtered retroactively

Why This Matters

• Users working across multiple codebases get inaccurate language/framework attributions
• The facet files currently contain no project identifier, making post-hoc filtering impossible
• After acting on insights recommendations, users have no way to measure improvement without a fresh baseline

Current Behaviour

• /insights analyses all sessions from the past ~30 days across all projects
• Facet JSON files have no project or cwd field
• No CLI flags exist for filtering or resetting