Submission Details: Collapsible two-column layout

[stepchud]

What/Why

Implements the collapsible two-column layout. Note this is a shared layout that will also be used on the evaluator's submission evaluation scoring view (#299 etc).

Figma Link

submission details

Acceptance Criteria

• Vertical blue bar separates the two columns when expanded
• Vertical blue bar moves to the right of the page and hides the solution submission data when collapsed
• See the note on Out of Scope

Disregard the following if this work does not include any UI changes

• WAVE screenshot
• Automated a11y tests (axe-rspec specs)
• Keyboard accessibility (tab navigation, form interactions)
• Responsiveness at desktop and mobile

Out of Scope

Additional interactivity on the left-hand column is out of scope, so that the two-column layout can be reused for submission scoring. It's okay to add static text and form elements but they will be no-op features that do not make any requests or updates to the backend.