UI improvements: responsive layout, unified panels, credit legend

- Add responsive 2-panel layout (mobile single-col, tablet/desktop grid)
- Unify specialization ranking with credit bars, status badges, and
  expandable allocation breakdowns (remove standalone ResultsDashboard)
- Inline decision tree ceiling data on course buttons with spec counts
- Add Clear All button to reset all course selections
- Add collapsible CreditLegend explaining bars, badges, and limits
- Extract ModeComparison and MutualExclusionWarnings to Notifications
- Add useMediaQuery hook with matchMedia-based breakpoint detection

openspec/changes/ui-improvements/specs/unified-specialization-panel/spec.md

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+## ADDED Requirements
+
+### Requirement: Specialization rows include credit progress
+Each specialization row in the ranking list SHALL display the credit progress bar and allocated/threshold credits alongside the rank, name, and status badge. The row layout SHALL be: reorder controls, rank number, name, credits (e.g. "7.5 / 9.0"), status badge, with a credit bar below.
+
+#### Scenario: Row displays allocated credits and bar
+- **WHEN** a specialization has 7.5 allocated credits from pinned courses
+- **THEN** the row SHALL show "7.5 / 9.0" and a credit progress bar filled to 7.5/9.0
+
+#### Scenario: Row displays zero credits
+- **WHEN** a specialization has no allocated credits
+- **THEN** the row SHALL show "0 / 9.0" and an empty credit progress bar with the 9-credit threshold marker visible
+
+### Requirement: Expandable allocation breakdown
+Achieved specialization rows SHALL be tappable/clickable to expand and show the allocation breakdown (which courses contribute how many credits).
+
+#### Scenario: Tap to expand achieved spec
+- **WHEN** a user taps an achieved specialization row
+- **THEN** the row SHALL expand to show a list of contributing courses and their credit amounts
+
+#### Scenario: Tap to collapse
+- **WHEN** a user taps an already-expanded achieved specialization row
+- **THEN** the allocation breakdown SHALL collapse
+
+#### Scenario: Non-achieved specs are not expandable
+- **WHEN** a user taps a specialization that is not achieved
+- **THEN** nothing SHALL happen (no expand/collapse)
+
+### Requirement: Achievement summary
+The panel SHALL display a summary count above the ranking list showing how many specializations are currently achieved.
+
+#### Scenario: Some achieved
+- **WHEN** 2 specializations are achieved
+- **THEN** the panel SHALL display "2 specializations achieved"
+
+#### Scenario: None achieved
+- **WHEN** no specializations are achieved
+- **THEN** the panel SHALL display "No specializations achieved yet"