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/ScenarioBPlanner.swift

@@ -32,6 +32,23 @@ import CoreLocation
 /// Scenario B: Selected games planning
 /// Input: selected_games, date_range (or trip_duration), optional must_stop
 /// Output: Itinerary options connecting all selected games with possible bonus games
+///
+/// - Expected Behavior:
+///   - No selected games → returns .failure with .noValidRoutes
+///   - No valid date ranges → returns .failure with .missingDateRange
+///   - GameFirst mode → uses sliding windows with gameFirstTripDuration
+///   - Explicit dateRange (non-gameFirst) → uses that range directly
+///   - All anchor games MUST appear in every valid route
+///   - Uses arrivalBeforeGameStart validator for travel segments
+///   - No routes satisfy constraints → .failure with .constraintsUnsatisfiable
+///   - Success → returns sorted itineraries based on leisureLevel
+///
+/// - Invariants:
+///   - Every returned route contains ALL selected (anchor) games
+///   - Anchor games cannot be dropped for geographic convenience
+///   - Sliding window always spans from first to last selected game
+///   - Date ranges always contain all selected game dates
+///
 final class ScenarioBPlanner: ScenarioPlanner {
 
     // MARK: - ScenarioPlanner Protocol
@@ -142,6 +159,14 @@ final class ScenarioBPlanner: ScenarioPlanner {
             // Deduplicate
             validRoutes = deduplicateRoutes(validRoutes)
 
+            // Filter routes to only include those containing ALL anchor games
+            // This is critical: regional search uses filtered anchors, so we must
+            // verify each route satisfies the original anchor constraint
+            validRoutes = validRoutes.filter { route in
+                let routeGameIds = Set(route.map { $0.id })
+                return anchorGameIds.isSubset(of: routeGameIds)
+            }
+
             // Build itineraries for each valid route
             for routeGames in validRoutes {
                 let stops = buildStops(from: routeGames, stadiums: request.stadiums)