Agent Skills: project-insights

Generate a Claude Code usage-insights report for a single project by analyzing its session transcripts. Use when the user wants per-project insights, a session-history retrospective, "what have I been doing in this repo", or a homegrown/markdown version of the built-in /insights. Mirrors the built-in /insights pipeline (per-session facet extraction -> aggregate facets -> at-a-glance) but scoped to one project and emitting markdown.