Improve warning headings and validation status clarity

During testing of the GitHub metadata import workflow, the validation/review UI displays warning headings and counts that are difficult to interpret.

Reviewers noted that labels such as "Needs attention," "done well," and "errors" do not clearly communicate what the associated counts represent. There is also some confusion between the warnings generated during metadata import and the warnings/errors displayed during metadata validation.

Additionally, required fields can appear as warnings or errors before the user has interacted with them. Required fields should be clearly indicated, but should not appear invalid simply because they have not yet been filled out or interacted with.

## Expected Behavior

- Warning and validation headings should clearly communicate what is being counted.
- Import warnings should be distinguishable from validation errors and fields requiring attention.
- Required fields should be visually marked as required without appearing invalid before user interaction.
- Validation status should be consistent and easy to understand.

## Acceptance Criteria

- [ ] Clarify the headings and labels used for warnings, errors, and validation status.
- [ ] Make the associated counts clearly correspond to the category being displayed.
- [ ] Distinguish import warnings from metadata validation errors.
- [ ] Prevent untouched required fields from appearing invalid before user interaction.
- [ ] Preserve the existing validation logic and behavior.
- [ ] Add or update tests covering the initial untouched state and warning/validation status display.

Start at the GitHub metadata import workflow's validation and review UI, then inspect the existing warning headings, counts, and required-field state. Add or update tests for the initial untouched state and status display; done means labels and counts are unambiguous, import warnings are distinct from validation errors, and untouched required fields are not invalid.

Written by the indexing model from the issue text.