Review my essay missing per-category preliminary grades

# Review my essay missing per-category preliminary grades

The "Review my essay" feature breaks the response down by category (content, organization, etc.) but doesn't assign per-category grades or a final grade.

## Reproduction

1. As a student or teacher, run "Review my essay" on a draft.
2. Observe that the categorical breakdown is present but no numeric grades are shown — neither per category nor an overall.

Specific case noted: one essay returned a 80/100 with a categorical breakdown; another returned the breakdown but no grades at all.

## Expected

Either (a) consistent per-category preliminary grades and a final, or (b) a clear product decision that this preview does not show grades and the GA does.

## Actual

Inconsistent — sometimes returns grades, sometimes doesn't.

## Impact

Low. Kevin noted on 2026-02-25 that "the grading assistant is so good right now that I don't think it matters." Worth verifying whether this feature is still needed at all once the GA is fully wired in, or whether it should be retired in favor of the GA.

## Affected versions

Reported 2026-02-25.

## Suspected cause

Two paths in the review pipeline — one returns category grades, one doesn't. Or the prompt occasionally fails to produce the structured output. Decide first whether to fix or deprecate.

## Workaround

Use the GA instead.