feat(09-03): exclude stadiums beyond end point in corridor filtering

Enhanced findDirectionalStadiums() to prevent including games at
stadiums that are beyond the destination city.

Previous behavior: Included stadiums like Seattle when planning
LA→Portland trips because Seattle was "making progress toward Portland"
(closer to Portland than LA is).

New behavior: Excludes stadiums where distance from start exceeds
the direct start→end distance (with 15% tolerance).

Example: LA→Portland trip now correctly excludes Seattle games
(Seattle is 1000mi from LA, Portland is 850mi from LA).

Fixes test: corridor_MultipleGamesMixed_FiltersCorrectly()

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

SportsTime/Planning/Engine/ScenarioCPlanner.swift

@@ -322,7 +322,11 @@ final class ScenarioCPlanner: ScenarioPlanner {
                 // Additional check: don't include if it's behind the start point
                 // (i.e., distance to end is greater than original distance)
                 if distanceToEnd <= directDistance * (1 + forwardProgressTolerance) {
-                    directionalIds.insert(id)
+                    // Final check: exclude stadiums that are beyond the end point
+                    // A stadium is beyond the end if it's farther from start than end is
+                    if toStadium <= directDistance * (1 + forwardProgressTolerance) {
+                        directionalIds.insert(id)
+                    }
                 }
             }
         }