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/ScenarioPlanner.swift

@@ -8,7 +8,12 @@
 import Foundation
 
 /// Protocol that all scenario planners must implement.
-/// Each scenario (A, B, C) has its own isolated implementation.
+/// Each scenario (A, B, C, D) has its own isolated implementation.
+///
+/// - Invariants:
+///   - Always returns either success or explicit failure, never throws
+///   - Success contains ranked itinerary options
+///   - Failure contains reason and any constraint violations
 protocol ScenarioPlanner {
 
     /// Plan itineraries for this scenario.
@@ -17,10 +22,24 @@ protocol ScenarioPlanner {
     func plan(request: PlanningRequest) -> ItineraryResult
 }
 
-/// Factory for creating the appropriate scenario planner
+/// Factory for creating the appropriate scenario planner.
+///
+/// - Expected Behavior:
+///   - followTeamId != nil → ScenarioDPlanner
+///   - selectedGames not empty → ScenarioBPlanner
+///   - startLocation AND endLocation != nil → ScenarioCPlanner
+///   - Otherwise → ScenarioAPlanner (default)
+///
+/// Priority order: D > B > C > A (first matching wins)
 enum ScenarioPlannerFactory {
 
-    /// Creates the appropriate planner based on the request inputs
+    /// Creates the appropriate planner based on the request inputs.
+    ///
+    /// - Expected Behavior:
+    ///   - followTeamId set → ScenarioDPlanner
+    ///   - selectedGames not empty → ScenarioBPlanner
+    ///   - Both start and end locations → ScenarioCPlanner
+    ///   - Otherwise → ScenarioAPlanner
     static func planner(for request: PlanningRequest) -> ScenarioPlanner {
         print("🔍 ScenarioPlannerFactory: Selecting planner...")
         print("   - followTeamId: \(request.preferences.followTeamId ?? "nil")")
@@ -51,7 +70,13 @@ enum ScenarioPlannerFactory {
         return ScenarioAPlanner()
     }
 
-    /// Classifies which scenario applies to this request
+    /// Classifies which scenario applies to this request.
+    ///
+    /// - Expected Behavior:
+    ///   - followTeamId set → .scenarioD
+    ///   - selectedGames not empty → .scenarioB
+    ///   - Both start and end locations → .scenarioC
+    ///   - Otherwise → .scenarioA
     static func classify(_ request: PlanningRequest) -> PlanningScenario {
         if request.preferences.followTeamId != nil {
             return .scenarioD