tune(map): raise thresholds — sub-square grid lines at zoom>=6 (was 5), field labels at zoom>=4 (was 3)

feature/map/src/main/java/com/rtbishop/look4sat/feature/map/MaidenheadGridOverlay.kt

@@ -312,8 +312,15 @@ class MaidenheadGridOverlay : Overlay() {
         const val FIELD_LON = 20.0
         const val SUB_SQUARE_LAT = 1.0
         const val SUB_SQUARE_LON = 2.0
-        const val GRID_ZOOM_SUB = 5.0
-        const val FIELD_ZOOM_LABELS = 3.0
+        // Zoom at which the 2°x1° sub-square grid lines/fills appear.
+        // 5.0 → 6.0: at zoom 5 a full field spans too little screen width and
+        // the sub-square grid is too dense to read; 6 roughly doubles the
+        // on-screen size of each square.
+        const val GRID_ZOOM_SUB = 6.0
+        // Zoom at which cell name labels appear.
+        // 3.0 → 4.0: fields were still cramped at zoom 3; 4 gives each 2-char
+        // field label comfortable room.
+        const val FIELD_ZOOM_LABELS = 4.0
         const val MIN_LABEL_CELL_PX = 48f
         const val MAX_OVERSHOOT_PX = 64
     }