refactor(tests): TDD rewrite of all unit tests with spec documentation

Complete rewrite of unit test suite using TDD methodology:

Planning Engine Tests:
- GameDAGRouterTests: Beam search, anchor games, transitions
- ItineraryBuilderTests: Stop connection, validators, EV enrichment
- RouteFiltersTests: Region, time window, scoring filters
- ScenarioA/B/C/D PlannerTests: All planning scenarios
- TravelEstimatorTests: Distance, duration, travel days
- TripPlanningEngineTests: Orchestration, caching, preferences

Domain Model Tests:
- AchievementDefinitionsTests, AnySportTests, DivisionTests
- GameTests, ProgressTests, RegionTests, StadiumTests
- TeamTests, TravelSegmentTests, TripTests, TripPollTests
- TripPreferencesTests, TripStopTests, SportTests

Service Tests:
- FreeScoreAPITests, RouteDescriptionGeneratorTests
- SuggestedTripsGeneratorTests

Export Tests:
- ShareableContentTests (card types, themes, dimensions)

Bug fixes discovered through TDD:
- ShareCardDimensions: mapSnapshotSize exceeded available width (960x480)
- ScenarioBPlanner: Added anchor game validation filter

All tests include:
- Specification tests (expected behavior)
- Invariant tests (properties that must always hold)
- Edge case tests (boundary conditions)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

SportsTime/Planning/Engine/ScenarioCPlanner.swift

@@ -38,6 +38,27 @@ import CoreLocation
 /// Scenario C: Directional route planning from start city to end city
 /// Input: start_location, end_location, day_span (or date_range)
 /// Output: Top 5 itinerary options with games along the directional route
+///
+/// - Expected Behavior:
+///   - No start location → returns .failure with .missingLocations
+///   - No end location → returns .failure with .missingLocations
+///   - Missing coordinates → returns .failure with .missingLocations
+///   - No stadiums in start city → returns .failure with .noGamesInRange
+///   - No stadiums in end city → returns .failure with .noGamesInRange
+///   - No valid date ranges → returns .failure with .missingDateRange
+///   - Directional filtering: only stadiums making forward progress included
+///   - Monotonic progress validation: route cannot backtrack significantly
+///   - Start and end locations added as non-game stops
+///   - No valid routes → .failure with .noValidRoutes
+///   - Success → returns sorted itineraries based on leisureLevel
+///
+/// - Invariants:
+///   - Start stop has no games and appears first
+///   - End stop has no games and appears last
+///   - All game stops are between start and end
+///   - Forward progress tolerance is 15%
+///   - Max detour distance is 1.5x direct distance
+///
 final class ScenarioCPlanner: ScenarioPlanner {
 
     // MARK: - Configuration