Keep the six map-source tiles on one row and follow the engine picker in the map tray gate

Sentinel-2 made the desktop source row wrap to two rows; the row now lays out every tile in one row (three columns on a phone, as before). scripts/qa-map-source-tray.mjs read the controller's removed imagery internals and counted five tiles between OSM and the styles; it now reads the live base provider and counts the section's tiles and engine picker. The five failures left also fail on origin/main e5d15f24.

src/panelStackLayout.test.mjs

@@ -267,7 +267,7 @@ test('expanded left panels integrate their headers with the container shell', ()
   );
 });
 
-test('Map Source uses five compact tiles in the bottom Visual Presets tray', async () => {
+test('Map Source keeps its compact tiles on one row in the bottom Visual Presets tray', async () => {
   const html = await renderApplicationHtml(readFileSync(new URL('../index.html', import.meta.url), 'utf8'));
   const css = readStylesheet(new URL('../style.css', import.meta.url));
 
@@ -275,8 +275,8 @@ test('Map Source uses five compact tiles in the bottom Visual Presets tray', asy
   assert.match(html, /id="control-panel"[\s\S]*?class="map-source-section"[\s\S]*?id="map-stack-chips"/);
   assert.match(
     css,
-    /\.map-stack-chip-row\s*\{[\s\S]*?grid-template-columns:\s*repeat\(5, minmax\(0, 1fr\)\);/,
-    'the desktop source selector keeps all five tiles on one row',
+    /\.map-stack-chip-row\s*\{[\s\S]*?grid-auto-flow:\s*column;\s*grid-auto-columns:\s*minmax\(0, 1fr\);/,
+    'the desktop source selector keeps every tile (six with Sentinel-2) on one row',
   );
 });
 

src/ui/styles/controls.css

@@ -815,7 +815,9 @@ html:not([lang='en']) .pp-slider-row > .pp-slider-mini-label {
 
 .map-stack-chip-row {
   display: grid;
-  grid-template-columns: repeat(5, minmax(0, 1fr));
+  /* One row, whatever the number of sources (six with Sentinel-2). */
+  grid-auto-flow: column;
+  grid-auto-columns: minmax(0, 1fr);
   gap: 4px;
 }
 
@@ -854,6 +856,7 @@ html:not([lang='en']) .pp-slider-row > .pp-slider-mini-label {
 
 @media (max-width: 620px) {
   .map-stack-chip-row {
+    grid-auto-flow: row;
     grid-template-columns: repeat(3, minmax(0, 1fr));
   }
 }