Student submission history

# Student submission history

Surface a student's released submissions from the document dashboard so they can see graded history without losing the document as the canonical writing surface.

## Problem

A student writes in `/app/documents/:id`. After submitting, the document dashboard shows the document but doesn't surface that submissions exist for it — let alone graded ones. Students lose track of feedback they've received.

## Goals (rough)

- Clicking a document on the dashboard always routes to `/app/documents/:id` (the editable sandbox stays the home base).
- If released submissions exist for that document, the document page shows a banner: "You have N graded submissions" with a link to the submissions list.
- The submissions list shows each submission's status and date.
- Clicking a submission opens `/app/submissions/:id` in view mode (read-only feedback, no editor unless [revision-flow](revision-flow.md) applies).

## Open questions

- [ ] Banner placement and dismissibility.
- [ ] Submissions list page layout — table, cards, timeline?
- [ ] Interaction with revision flow once that ships (chains vs. flat list).

## Engineering handoff

Not ready. Needs UX walkthrough, edge cases, and decision on submissions list layout.