fix(tours): keep the city walk helpers only their own files use inside them (CW-01, CW-03, CW-04)

The filter for a walk's stations in the planner, the opening windows of a
walk's schedule and the station shape of a walk's progress were exported,
although nothing outside their own file reads them, so the check for unused
exports counted three more than it allows. They are local to their files now;
a city walk plans, checks off and times its stops as before.

client/src/components/Tours/planner/stationModel.ts

@@ -19,7 +19,7 @@ export interface WalkTimes {
 }
 
 /** The stations of a city walk: its points that are no shaping points. */
-export function stationsOf(points: readonly TourPlannerWaypoint[]): TourPlannerWaypoint[] {
+function stationsOf(points: readonly TourPlannerWaypoint[]): TourPlannerWaypoint[] {
   return points.filter((point) => !point.shaping);
 }
 

client/src/components/Tours/walk/walkSchedule.ts

@@ -49,7 +49,7 @@ function daysOf(spec: string): Set<number> | null {
 }
 
 /** The windows a place is open on a date, in minutes; null where the hours cannot be read. */
-export function openWindows(hours: string, date: string): Array<[number, number]> | null {
+function openWindows(hours: string, date: string): Array<[number, number]> | null {
   const weekday = weekdayOf(date);
   if (weekday === null) return null;
   const text = hours.trim();

server/src/nest/tours/tour-visits.service.ts

@@ -111,7 +111,7 @@ export class TourVisitsService {
 }
 
 /** CW-09: one station of a walk on a day, as an assistant reads it. */
-export interface WalkProgressStation {
+interface WalkProgressStation {
   position: number;
   name: string | null;
   lat: number;