Avoid cached manifest downloads

- Prevent `upgrade --ask` from repeating bottle manifest headings
  when the prompt already fetched valid bottle manifests
- Validate cached bottle manifests quietly before skipping queue work
  so corrupt caches are cleared and retried through existing fetch logic
- Add `HOMEBREW_NO_ASK` as a documented no-op placeholder
  until ask mode becomes the default in a later release
- Avoid global path stubs affecting Bundle dump formula setup
- Cover cached manifest handling in `upgrade` and `FormulaInstaller`