## Why

Users selecting elective courses have no way to see course descriptions or instructor information within the app. They must cross-reference a separate PDF document to understand what each course covers. Adding inline course info popups reduces friction and helps users make more informed selections.

## What Changes

- Add a new data file mapping each course ID to its description text and instructor list, extracted from the J27 Electives PDF and supplementary sources
- Add an info icon `(i)` next to each course name in the course selection UI
- Clicking/tapping the info icon opens a popover displaying the course description and instructor(s)
- Popover closes on click outside, clicking the icon again, or pressing Escape
- Works identically on desktop and mobile (no hover/long-press distinction)

## Capabilities

### New Capabilities
- `course-info-popover`: Inline popover UI triggered by an info icon on each course, displaying course description and instructor(s) from a static data source

### Modified Capabilities

## Impact

- New file: `app/src/data/courseDescriptions.ts` — static data (~35 course entries with descriptions and instructor arrays)
- Modified: `app/src/data/types.ts` — no changes needed (data lives in separate lookup, not on Course type)
- Modified: `app/src/components/CourseSelection.tsx` — add info icon and popover component
- No solver, state, or worker changes
- No new dependencies