feat(planner): open places and day routes in CoMaps

Add CoMaps, the offline OpenStreetMap navigator, alongside the existing
map integrations. A geolocated place gains a CoMaps entry in its
navigation menu, and a day's route toolbar gains a button that hands the
day's bookended stops to CoMaps in that day's travel mode.

CoMaps' route link carries only a start and a destination, so a two-stop
day goes as a route and a longer one as named pins rather than silently
losing the stops in between. Links use the https form so a device without
CoMaps installed lands on comaps.at instead of a dead scheme.

The hotel-bookend logic behind the Google Maps export was duplicated
between desktop and mobile; both now share dayExportStops so the two
links cannot disagree about which hotel legs are real.

Addresses discussion #1904

client/src/components/Map/RouteCalculator.test.ts

@@ -9,6 +9,7 @@ import {
   calculateSegments,
   optimizeRoute,
   generateGoogleMapsUrl,
+  generateCoMapsUrl,
   parsePluginProfile,
   withHotelBookends,
 } from './RouteCalculator'
@@ -572,3 +573,43 @@ describe('calculateRouteWithLegs cache eviction', () => {
     expect(hits).toBe(1)
   })
 })
+
+// ── generateCoMapsUrl ─────────────────────────────────────────────────────────
+
+describe('generateCoMapsUrl', () => {
+  const eiffel = { lat: 48.8584, lng: 2.2945, name: 'Eiffel Tower' }
+  const louvre = { lat: 48.8606, lng: 2.3376, name: 'Louvre' }
+  const notre = { lat: 48.8530, lng: 2.3499, name: 'Notre-Dame' }
+
+  it('FE-COMP-ROUTECALCULATOR-016: no stops, no link', () => {
+    expect(generateCoMapsUrl([])).toBeNull()
+  })
+
+  it('FE-COMP-ROUTECALCULATOR-017: two stops build a real route, mode included', () => {
+    expect(generateCoMapsUrl([eiffel, louvre], 'walking')).toBe(
+      'https://comaps.at/route?sll=48.8584,2.2945&saddr=Eiffel%20Tower'
+      + '&dll=48.8606,2.3376&daddr=Louvre&type=pedestrian',
+    )
+  })
+
+  it('FE-COMP-ROUTECALCULATOR-018: TREK profiles map onto CoMaps travel modes', () => {
+    expect(generateCoMapsUrl([eiffel, louvre], 'driving')).toContain('type=vehicle')
+    expect(generateCoMapsUrl([eiffel, louvre], 'cycling')).toContain('type=bicycle')
+    // A plugin router has no CoMaps equivalent, so it falls back rather than
+    // sending a mode CoMaps would reject.
+    expect(generateCoMapsUrl([eiffel, louvre], 'plugin:ev/fast')).toContain('type=vehicle')
+  })
+
+  it('FE-COMP-ROUTECALCULATOR-019: three stops go as pins, because a route link would drop the middle', () => {
+    const url = generateCoMapsUrl([eiffel, louvre, notre])!
+    expect(url).toBe(
+      'https://comaps.at/map?v=1&ll=48.8584,2.2945&n=Eiffel%20Tower'
+      + '&ll=48.8606,2.3376&n=Louvre&ll=48.853,2.3499&n=Notre-Dame',
+    )
+  })
+
+  it('FE-COMP-ROUTECALCULATOR-020: a single stop is a pin, and a nameless one is labelled by position', () => {
+    expect(generateCoMapsUrl([{ lat: 48.85, lng: 2.35 }]))
+      .toBe('https://comaps.at/map?v=1&ll=48.85,2.35&n=48.85%2C2.35')
+  })
+})

client/src/components/Map/RouteCalculator.ts

@@ -116,6 +116,42 @@ export function generateGoogleMapsUrl(places: Waypoint[]): string | null {
   return `https://www.google.com/maps/dir/${stops}`
 }
 
+/** A stop that can carry its name into a deep link that has somewhere to put one. */
+export type NamedWaypoint = Waypoint & { name?: string | null }
+
+/** TREK's route profiles in CoMaps' vocabulary; a plugin profile has no equivalent and drives. */
+function coMapsRouteType(profile: RouteProfileKey): string {
+  if (profile === 'walking') return 'pedestrian'
+  if (profile === 'cycling') return 'bicycle'
+  return 'vehicle'
+}
+
+/**
+ * Open a day's stops in CoMaps for offline navigation (#1904).
+ *
+ * CoMaps has two links and they trade against each other. `route` builds real
+ * turn-by-turn in the given travel mode but takes a start and a destination and
+ * nothing between them; `map` takes any number of named pins but routes nothing.
+ * So a two-stop day goes as a route — everything it has fits, mode included —
+ * and a longer one goes as pins, because handing over the whole day and letting
+ * CoMaps route leg by leg beats quietly dropping the middle of someone's plan.
+ * A day that needs the full itinerary as one navigable track has the GPX export.
+ *
+ * https rather than `cm://` for the same reason as `getCoMapsUrlForPlace`.
+ */
+export function generateCoMapsUrl(places: NamedWaypoint[], profile: RouteProfileKey = 'driving'): string | null {
+  const valid = places.filter((p) => p.lat != null && p.lng != null)
+  if (valid.length === 0) return null
+  const label = (p: NamedWaypoint) => encodeURIComponent(p.name?.trim() || `${p.lat},${p.lng}`)
+  if (valid.length === 2) {
+    const [from, to] = valid
+    return `https://comaps.at/route?sll=${from.lat},${from.lng}&saddr=${label(from)}`
+      + `&dll=${to.lat},${to.lng}&daddr=${label(to)}&type=${coMapsRouteType(profile)}`
+  }
+  const pins = valid.map((p) => `ll=${p.lat},${p.lng}&n=${label(p)}`).join('&')
+  return `https://comaps.at/map?v=1&${pins}`
+}
+
 // Squared planar distance — enough for nearest-neighbor comparisons and cheaper than a full haversine.
 function sqDist(a: Waypoint, b: Waypoint): number {
   return (a.lat - b.lat) ** 2 + (a.lng - b.lng) ** 2