repopo: Improve CLI UX: Progress Indicators & Verbosity

[tylerbutler]

The CLI currently lacks feedback for long-running operations and has confusing verbosity flags.

Action Items:

• Add a progress spinner (e.g., ora) during file processing.
• Fix inverted verbosity logic: --quiet should suppress output, --verbose should add detail. Currently verbose prevents stats.
• Add a summary output on success (e.g., "✓ All policies passed").
• Clarify usage of check vs check-native in help text.

[tylerbutler]

Research completed on progress spinners.

Recommendation: Use nanospinner

• Zero New Dependencies: It only depends on picocolors, which repopo already uses.
• Minimal Size: ~10KB unpacked.
• Zero Config: Simple API (spin(), success(), error()).

Why not Consola?
We investigated updating consola (currently v3.4.0), but it does not include a built-in animated progress spinner, only static log types. Adding a heavy spinner library like ora would pull in 5+ unnecessary dependencies.