fix: passengers now board/disembark based on their car position, not locomotive

Previously, passengers would board/disembark when the locomotive reached their
station, which was incorrect. Now:

**Boarding:**
- Passengers board when an EMPTY train car reaches their origin station
- Each passenger is assigned to the first available empty car (0-4)
- Car position calculated as: trainPosition - (carIndex + 1) * 7%

**Disembarking:**
- Passengers disembark when THEIR specific car reaches their destination
- Uses the passenger's position in the boardedPassengers array to find car index
- Each passenger's car position is independently checked against their destination

This creates more realistic train behavior where passengers interact with
individual train cars rather than just the locomotive.

Removed unused imports: findBoardablePassengers, findDeliverablePassengers

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

apps/web/src/app/games/complement-race/hooks/useSteamJourney.ts

@@ -1,6 +1,6 @@
 import { useEffect, useRef } from 'react'
 import { useComplementRace } from '../context/ComplementRaceContext'
-import { generatePassengers, findBoardablePassengers, findDeliverablePassengers } from '../lib/passengerGenerator'
+import { generatePassengers } from '../lib/passengerGenerator'
 import { useSoundEffects } from './useSoundEffects'
 
 /**
@@ -101,34 +101,59 @@ export function useSteamJourney() {
       })
 
       // Check for passengers that should board
-      const boardable = findBoardablePassengers(
-        state.passengers,
-        state.stations,
-        trainPosition
-      )
+      // Passengers board when an EMPTY car reaches their station
+      const CAR_SPACING = 7 // Must match SteamTrainJourney component
+      const MAX_CARS = 5
+      const currentBoardedPassengers = state.passengers.filter(p => p.isBoarded && !p.isDelivered)
 
-      // Board passengers at their origin station
-      boardable.forEach(passenger => {
-        dispatch({
-          type: 'BOARD_PASSENGER',
-          passengerId: passenger.id
-        })
+      // Find waiting passengers whose origin station has an empty car nearby
+      state.passengers.forEach(passenger => {
+        if (passenger.isBoarded || passenger.isDelivered) return
+
+        const station = state.stations.find(s => s.id === passenger.originStationId)
+        if (!station) return
+
+        // Check if any empty car is at this station
+        // Cars are at positions: trainPosition - 7, trainPosition - 14, etc.
+        for (let carIndex = 0; carIndex < MAX_CARS; carIndex++) {
+          // Skip if this car already has a passenger
+          if (currentBoardedPassengers[carIndex]) continue
+
+          const carPosition = Math.max(0, trainPosition - (carIndex + 1) * CAR_SPACING)
+          const distance = Math.abs(carPosition - station.position)
+
+          // If car is at station (within 3% tolerance), board this passenger
+          if (distance < 3) {
+            dispatch({
+              type: 'BOARD_PASSENGER',
+              passengerId: passenger.id
+            })
+            return // Board this passenger and move on
+          }
+        }
       })
 
       // Check for deliverable passengers
-      const deliverable = findDeliverablePassengers(
-        state.passengers,
-        state.stations,
-        trainPosition
-      )
+      // Passengers disembark when THEIR car reaches their destination
+      currentBoardedPassengers.forEach((passenger, carIndex) => {
+        if (!passenger || passenger.isDelivered) return
 
-      // Deliver passengers at stations
-      deliverable.forEach(({ passenger, points }) => {
-        dispatch({
-          type: 'DELIVER_PASSENGER',
-          passengerId: passenger.id,
-          points
-        })
+        const station = state.stations.find(s => s.id === passenger.destinationStationId)
+        if (!station) return
+
+        // Calculate this passenger's car position
+        const carPosition = Math.max(0, trainPosition - (carIndex + 1) * CAR_SPACING)
+        const distance = Math.abs(carPosition - station.position)
+
+        // If this car is at the destination station (within 3% tolerance), deliver
+        if (distance < 3) {
+          const points = passenger.isUrgent ? 20 : 10
+          dispatch({
+            type: 'DELIVER_PASSENGER',
+            passengerId: passenger.id,
+            points
+          })
+        }
       })
 
       // Check for route completion (entire train exits tunnel)