Show folder breakdowns in dispatch stats

[jongio]

dispatch stats already groups by repository, branch, and host. Folder counts would help users spot active local workspaces, especially when multiple repos or forks share similar names.

Acceptance criteria:

• Text, JSON, CSV, and Markdown stats include a folder breakdown.
• --top applies to folder counts too.
• Empty folder values use the same fallback style as other breakdowns.
• Tests cover the new breakdown.

[jongio]

Current scan still ranks this as useful for people using stats to spot active local workspaces. It should use the same output shapes as the existing repository, branch, and host type sections.