Add facet classification segment generator with priority support
- Add priority-based ordering to run_generators_via_cortex() so generators
can depend on outputs from earlier generators (lower priority runs first)
- Create muse/facets.md segment generator (priority 90) that classifies
segment activity into facets based on other segment outputs
- Uses tier 3 (LITE) model with agents-only sources for fast/cheap inference
- Update muse CLI to display priority field prominently
- Document generator priority support in CORTEX.md with recommended ranges
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>