Teacher grammar issue actions

# Teacher grammar issue actions

Let a teacher remove an AI grammar/style correction from a graded submission before releasing the grade, while keeping the existing hide/show-all decluttering control for teachers and students.

## Source context

Email thread "Allow Teachers to Hide Grammar/Style Comments" landed on this product shape:

- Students keep the existing read-only hover tooltip: issue kind, message, and rule.
- Teachers in grading mode get a direct action on the highlighted grammar issue.
- The final teacher action should be "Remove comment" on the issue itself, not a confusing mix of hide/remove/hide-all actions in the tooltip.
- The existing Hide all / Show all control under the Grammar/Syntax rubric remains for temporary decluttering.

Brian explicitly asked to queue this for deployment after Kevin's revised prototype.

## Current status

`yawp-2.0` PR #106 is open with green checks. It is ready for final review against this behavior, then merge if the implementation matches the simplified action model.

## Goals

- Teacher can remove an AI grammar/style correction from an unreleased graded submission.
- Removed corrections do not appear to the student after grade release.
- Hide/show-all remains temporary view state, not a permanent content edit.
- Student view stays unchanged unless a teacher removed the correction before release.

## Non-goals

- Persisting per-teacher "hide this one issue" state across reloads.
- Applying the same treatment to yellow grade-comment highlights in this pass.
- Letting students remove or hide individual AI corrections from the authoritative graded artifact.

## Test plan

- Teacher in grading mode sees a Remove comment action on grammar/style issue hover.
- Teacher removes an issue; it disappears from the release artifact and does not reappear after reload.
- Student/read-only view has no action buttons.
- Hide all / Show all still only hides or shows the grammar layer temporarily.
- Released submissions cannot be modified through this action.