fix(map): scope first-call labels to the selected operated grid (台址)

core/domain/src/main/java/com/rtbishop/look4sat/core/domain/model/GridQso.kt

@@ -131,3 +131,13 @@ fun GridQso.stationGridSetKey(): String? =
  */
 fun List<GridQso>.scopedToStation(stationId: String?): List<GridQso> =
     if (stationId == null) this else filter { it.stationGridSetKey() == stationId }
+
+/**
+ * For every grid in the store, the callsign of the earliest QSO — scoped to the
+ * operated-grid selector's choice first, so a specific 台址 labels each worked
+ * cell with ITS first contact; null ("All") keeps the global first call.
+ */
+fun Map<String, List<GridQso>>.firstCallsByGrid(stationId: String?): Map<String, String> =
+    mapNotNull { (grid, qsos) ->
+        qsos.scopedToStation(stationId).minByOrNull { it.epochMs }?.let { grid to it.call }
+    }.toMap()

core/domain/src/test/java/com/rtbishop/look4sat/core/domain/model/GridQsoStationScopeTest.kt

@@ -94,4 +94,35 @@ class GridQsoStationScopeTest {
         val list = listOf(qso("A", myGrid = "OL62"))
         assertEquals(emptyList<GridQso>(), list.scopedToStation("PM01"))
     }
+
+    // --- firstCallsByGrid ---
+
+    @Test
+    fun `first call per grid picks the earliest of the scoped records`() {
+        val store = mapOf(
+            "OL62" to listOf(
+                qso("OTHER", myGrid = "PM01").copy(epochMs = 10),
+                qso("MINE", myGrid = "OL62").copy(epochMs = 20)
+            ),
+            "PM95" to listOf(qso("MINE2", myGrid = "OL62").copy(epochMs = 30))
+        )
+        assertEquals(mapOf("OL62" to "MINE", "PM95" to "MINE2"), store.firstCallsByGrid("OL62"))
+    }
+
+    @Test
+    fun `first call per grid with All uses every record`() {
+        val store = mapOf(
+            "OL62" to listOf(
+                qso("OTHER", myGrid = "PM01").copy(epochMs = 10),
+                qso("MINE", myGrid = "OL62").copy(epochMs = 20)
+            )
+        )
+        assertEquals(mapOf("OL62" to "OTHER"), store.firstCallsByGrid(null))
+    }
+
+    @Test
+    fun `grids without scoped records get no first call`() {
+        val store = mapOf("OL62" to listOf(qso("A", myGrid = "PM01")))
+        assertEquals(emptyMap<String, String>(), store.firstCallsByGrid("OL62"))
+    }
 }