## ADDED Requirements

### Requirement: Collapsible credit legend
The specialization panel SHALL include a collapsible "How to read this" section that explains the credit bars and status badges.

#### Scenario: Legend collapsed by default
- **WHEN** the page loads
- **THEN** the legend SHALL be collapsed, showing only a "How to read this" toggle link

#### Scenario: Expand legend
- **WHEN** the user clicks "How to read this"
- **THEN** the legend SHALL expand to show explanations of credit bar segments, the 9-credit threshold marker, and status badge meanings

#### Scenario: Collapse legend
- **WHEN** the user clicks the toggle while the legend is expanded
- **THEN** the legend SHALL collapse back to just the toggle link

### Requirement: Legend content
The legend SHALL explain: the dark bar segment represents credits allocated from pinned courses, the light bar segment represents potential credits from open sets, the tick mark represents the 9-credit threshold required for a specialization, and the four status badges (Achieved, Achievable, Missing Req., Unreachable) with their meanings.

#### Scenario: Legend describes all elements
- **WHEN** the legend is expanded
- **THEN** it SHALL contain descriptions for: allocated credits bar, potential credits bar, threshold marker, and all four status badge types

### Requirement: Legend state is not persisted
The legend expanded/collapsed state SHALL reset to collapsed on page reload.

#### Scenario: Reset on reload
- **WHEN** the user expands the legend and reloads the page
- **THEN** the legend SHALL be collapsed