Improve desktop geolocation handling

src/uk_bus_stops/static/app.js

@@ -605,8 +605,17 @@ byId('locate-button').addEventListener('click', () => {
       const apiParams = new URLSearchParams({...coordinates, label: 'Your location'});
       loadUrl(`${API_URLS.stops}?${apiParams}`);
     },
-    () => { setLoading(false); showError('Location access was denied or unavailable.'); },
+    error => {
-    {enableHighAccuracy: true, timeout: 10000}
+      setLoading(false);
+      const messages = {
+        1: 'Location permission was denied. Check this site’s location permission in your browser.',
+        2: 'Your browser could not determine your location. Check that device or operating-system location services are enabled.',
+        3: 'Determining your location timed out. Try again, or enter latitude and longitude manually.',
+      };
+      showError(messages[error.code] || `Could not determine your location${error.message ? `: ${error.message}` : '.'}`);
+    },
+    // Desktop browsers usually rely on network location rather than GPS.
+    {enableHighAccuracy: false, timeout: 20000, maximumAge: 300000}
   );
 });
 

tests/test_uk_bus_stops_playwright.py

@@ -219,6 +219,23 @@ def test_single_postcode_match_opens_directly(chromium_browser: Any, flask_url:
     page.close()
 
 
+def test_browser_location_loads_nearby_stops(chromium_browser: Any, flask_url: str) -> None:
+    """A permitted desktop geolocation result is used for a nearby-stop search."""
+    context = chromium_browser.new_context(geolocation={"latitude": 51.5, "longitude": -0.12})
+    context.grant_permissions(["geolocation"], origin=flask_url)
+    page = context.new_page()
+    page.route("**/api/stops?*", lambda route: route.fulfill(json={
+        "kind": "location",
+        "location": {"lat": 51.5, "lon": -0.12, "label": "Your location"},
+        "stops": [],
+    }))
+    page.goto(flask_url, wait_until="networkidle")
+    page.get_by_role("button", name="Use my current location").click()
+    playwright_api.expect(page).to_have_url(re.compile(r"\?lat=51.5&lon=-0.12$"))
+    playwright_api.expect(page.locator("#stop-count")).to_have_text("0 found")
+    context.close()
+
+
 def test_mobile_layout_opens_results_sheet(chromium_browser: Any, flask_url: str) -> None:
     """The finder exposes its search panel as an open mobile bottom sheet."""
     page = chromium_browser.new_page(viewport={"width": 390, "height": 844})