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/ScenarioDPlanner.swift

@@ -29,6 +29,22 @@ import CoreLocation
 ///   We find: @Red Sox (Jan 5), @Blue Jays (Jan 8), vs Orioles (Jan 12)
 ///   Output: Route visiting Boston → Toronto → New York
 ///
+/// - Expected Behavior:
+///   - No followTeamId → returns .failure with .missingTeamSelection
+///   - No date range → returns .failure with .missingDateRange
+///   - No team games found → returns .failure with .noGamesInRange
+///   - No games in date range/region → returns .failure with .noGamesInRange
+///   - filterToTeam returns BOTH home and away games for the team
+///   - With selectedRegions → only includes games in those regions
+///   - No valid routes → .failure with .noValidRoutes
+///   - All routes fail constraints → .failure with .constraintsUnsatisfiable
+///   - Success → returns sorted itineraries based on leisureLevel
+///
+/// - Invariants:
+///   - All returned games have homeTeamId == teamId OR awayTeamId == teamId
+///   - Games are chronologically ordered within each stop
+///   - Duplicate routes are removed
+///
 final class ScenarioDPlanner: ScenarioPlanner {
 
     // MARK: - ScenarioPlanner Protocol