fix: ScenarioCPlanner endpoint merging and game validation

Eliminate redundant 0-mile travel segments when start/end city matches
the first/last game stop city, and fail early when no games exist at
endpoint cities within the selected date range.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

SportsTime/Planning/Engine/ScenarioCPlanner.swift

@@ -162,6 +162,38 @@ final class ScenarioCPlanner: ScenarioPlanner {
             )
         }
 
+        // ──────────────────────────────────────────────────────────────────
+        // Step 2.5: Validate games exist at endpoint stadiums (explicit date range)
+        // ──────────────────────────────────────────────────────────────────
+        if let dateRange = request.dateRange {
+            let startStadiumIds = Set(startStadiums.map { $0.id })
+            let endStadiumIds = Set(endStadiums.map { $0.id })
+
+            let hasStartGames = request.allGames.contains {
+                startStadiumIds.contains($0.stadiumId) && dateRange.contains($0.startTime)
+            }
+            let hasEndGames = request.allGames.contains {
+                endStadiumIds.contains($0.stadiumId) && dateRange.contains($0.startTime)
+            }
+
+            if !hasStartGames {
+                return .failure(PlanningFailure(
+                    reason: .noGamesInRange,
+                    violations: [ConstraintViolation(type: .general,
+                        description: "No games found at \(startLocation.name) within the selected dates",
+                        severity: .error)]
+                ))
+            }
+            if !hasEndGames {
+                return .failure(PlanningFailure(
+                    reason: .noGamesInRange,
+                    violations: [ConstraintViolation(type: .general,
+                        description: "No games found at \(endLocation.name) within the selected dates",
+                        severity: .error)]
+                ))
+            }
+        }
+
         // ──────────────────────────────────────────────────────────────────
         // Step 3: Generate date ranges
         // ──────────────────────────────────────────────────────────────────
@@ -544,6 +576,8 @@ final class ScenarioCPlanner: ScenarioPlanner {
     }
 
     /// Builds stops with start and end location endpoints.
+    /// Skips adding a separate endpoint stop when the first/last game stop
+    /// is already in the same city, avoiding redundant 0-mile travel segments.
     private func buildStopsWithEndpoints(
         start: LocationInput,
         end: LocationInput,
@@ -551,43 +585,58 @@ final class ScenarioCPlanner: ScenarioPlanner {
         stadiums: [String: Stadium]
     ) -> [ItineraryStop] {
 
+        // Build game stops first so we can check for city overlap
+        let gameStops = buildStops(from: games, stadiums: stadiums)
+
         var stops: [ItineraryStop] = []
 
-        // Start stop (no games)
-        let startArrival = games.first?.gameDate.addingTimeInterval(-86400) ?? Date()
-        let startStop = ItineraryStop(
-            city: start.name,
-            state: "",
-            coordinate: start.coordinate,
-            games: [],
-            arrivalDate: startArrival,
-            departureDate: startArrival,
-            location: start,
-            firstGameStart: nil
-        )
-        stops.append(startStop)
+        // Only add start endpoint if start city differs from first game stop city
+        let firstGameCity = gameStops.first?.city
+        if firstGameCity == nil || !citiesMatch(start.name, firstGameCity!) {
+            let startArrival = games.first?.gameDate.addingTimeInterval(-86400) ?? Date()
+            let startStop = ItineraryStop(
+                city: start.name,
+                state: "",
+                coordinate: start.coordinate,
+                games: [],
+                arrivalDate: startArrival,
+                departureDate: startArrival,
+                location: start,
+                firstGameStart: nil
+            )
+            stops.append(startStop)
+        }
 
-        // Game stops
-        let gameStops = buildStops(from: games, stadiums: stadiums)
         stops.append(contentsOf: gameStops)
 
-        // End stop (no games)
-        let endArrival = games.last?.gameDate.addingTimeInterval(86400) ?? Date()
-        let endStop = ItineraryStop(
-            city: end.name,
-            state: "",
-            coordinate: end.coordinate,
-            games: [],
-            arrivalDate: endArrival,
-            departureDate: endArrival,
-            location: end,
-            firstGameStart: nil
-        )
-        stops.append(endStop)
+        // Only add end endpoint if end city differs from last game stop city
+        let lastGameCity = gameStops.last?.city
+        if lastGameCity == nil || !citiesMatch(end.name, lastGameCity!) {
+            let endArrival = games.last?.gameDate.addingTimeInterval(86400) ?? Date()
+            let endStop = ItineraryStop(
+                city: end.name,
+                state: "",
+                coordinate: end.coordinate,
+                games: [],
+                arrivalDate: endArrival,
+                departureDate: endArrival,
+                location: end,
+                firstGameStart: nil
+            )
+            stops.append(endStop)
+        }
 
         return stops
     }
 
+    /// Checks if two city names refer to the same city using normalized comparison.
+    private func citiesMatch(_ cityA: String, _ cityB: String) -> Bool {
+        let a = normalizeCityName(cityA)
+        let b = normalizeCityName(cityB)
+        if a == b { return true }
+        return a.contains(b) || b.contains(a)
+    }
+
     // MARK: - Monotonic Progress Validation
 
     /// Validates that the route makes generally forward progress toward the end.