fix: transponder filters - mutual exclusion and beacon-free fallback

Two correctness fixes for the FM/Linear/SSTV filters:

1. Satellite type picker: virtual transponder types (AMSAT Live FM,
   AMSAT Live Linear, Live SSTV) are now mutually exclusive with the
   regular TLE-source types - ticking a virtual type clears Amateur/
   CubeSat/etc and vice versa, so selecting 'AMSAT Live FM' no longer
   unions in hundreds of non-transponder satellites. Virtual types
   still combine with each other. Also: an empty virtual-type resolve
   now yields an empty list instead of falling back to 'show all'.

2. Mutual-match fallback: when the AMSAT lists are empty (first run /
   sync failure) the DB mode filter used downlinkMode alone, so any
   downlink-only beacon sharing a mode label was misclassified
   (ISS/IO-86 CW beacons into Linear, FO-29's FM Digitalker into FM).
   New getIdsWithModesAndUplink() requires uplinkLow IS NOT NULL,
   matching real transponders only. SSTV filter keeps the old query
   (SSTV sats are often downlink-only).

Shared virtual-type names moved to Sources.virtualTypeNames.

core/data/src/main/java/com/rtbishop/look4sat/core/data/database/Look4SatDao.kt

@@ -48,6 +48,12 @@ interface Look4SatDao {
     @Query("SELECT catnum FROM radios WHERE downlinkMode IN (:modes) AND isAlive = 1")
     suspend fun getIdsWithModes(modes: List<String>): List<Int>
 
+    /** Like [getIdsWithModes] but only matches transponder records with an uplink,
+     *  excluding downlink-only beacons/telemetry that share the same mode label
+     *  (e.g. CW beacons, FM voice-synthesis beacons) from FM/Linear filter fallback. */
+    @Query("SELECT catnum FROM radios WHERE downlinkMode IN (:modes) AND uplinkLow IS NOT NULL AND isAlive = 1")
+    suspend fun getIdsWithModesAndUplink(modes: List<String>): List<Int>
+
     @Query("SELECT COUNT(*) FROM radios")
     suspend fun getRadiosTotal(): Int
 

core/data/src/main/java/com/rtbishop/look4sat/core/data/repository/SatelliteRepo.kt

@@ -67,6 +67,8 @@ class SatelliteRepo(
 
     override suspend fun getSatelliteIdsWithModes(modes: List<String>) = localStorage.getIdsWithModes(modes)
 
+    override suspend fun getSatelliteIdsWithModesAndUplink(modes: List<String>) = localStorage.getIdsWithModesAndUplink(modes)
+
     override suspend fun initRepository() = withContext(dispatcher) {
         combine(
             settingsRepo.selectedIds,

core/data/src/main/java/com/rtbishop/look4sat/core/data/repository/SelectionRepo.kt

@@ -50,7 +50,7 @@ class SelectionRepo(
             null // null = no filtering
         } else {
             val ids = resolveTypeIds(types)
-            if (ids.isEmpty()) null else ids.toHashSet()
+            if (ids.isEmpty()) emptySet() else ids.toHashSet()
         }
         currentItems.map { items ->
             if (catnumSet == null) items else items.filter { it.catnum in catnumSet }
@@ -72,9 +72,9 @@ class SelectionRepo(
         val idsSet = mutableSetOf<Int>()
         types.forEach { type ->
             when (type) {
-                "AMSAT Live FM" -> idsSet.addAll(settingsRepo.getAmSatFmCatnums())
-                "AMSAT Live Linear" -> idsSet.addAll(settingsRepo.getAmSatLinearCatnums())
-                "Live SSTV" -> idsSet.addAll(localSource.getIdsWithModes(listOf("SSTV")))
+                Sources.virtualTypeNames[0] -> idsSet.addAll(settingsRepo.getAmSatFmCatnums())
+                Sources.virtualTypeNames[1] -> idsSet.addAll(settingsRepo.getAmSatLinearCatnums())
+                Sources.virtualTypeNames[2] -> idsSet.addAll(localSource.getIdsWithModes(listOf("SSTV")))
                 else -> idsSet.addAll(settingsRepo.getSatelliteTypesIds(listOf(type)))
             }
         }
@@ -83,7 +83,7 @@ class SelectionRepo(
 
     override fun getTypesList() = buildList {
         // 三个转发器/活动虚拟类型排在最前.
-        addAll(listOf("AMSAT Live FM", "AMSAT Live Linear", "Live SSTV"))
+        addAll(Sources.virtualTypeNames)
         addAll(Sources.satelliteDataUrls.keys.sorted().toMutableList().apply { removeAt(0) })
     }
 

core/data/src/main/java/com/rtbishop/look4sat/core/data/source/LocalSource.kt

@@ -48,6 +48,7 @@ class LocalSource(private val look4SatDao: Look4SatDao) : ILocalSource {
     override suspend fun deleteEntries() = look4SatDao.deleteEntries()
 
     override suspend fun getIdsWithModes(modes: List<String>) = look4SatDao.getIdsWithModes(modes)
+    override suspend fun getIdsWithModesAndUplink(modes: List<String>) = look4SatDao.getIdsWithModesAndUplink(modes)
 
     private fun FrameworkEntry.toDomain() = OrbitalData(
         this.name, this.epoch, this.meanmo, this.eccn, this.incl,

core/data/src/test/java/com/rtbishop/look4sat/core/data/repository/DatabaseRepoTest.kt

@@ -180,6 +180,7 @@ private class FakeLocalSource : ILocalSource {
     }
 
     override suspend fun getIdsWithModes(modes: List<String>): List<Int> = emptyList()
+    override suspend fun getIdsWithModesAndUplink(modes: List<String>): List<Int> = emptyList()
 
     override suspend fun getRadiosTotal(): Int = insertedRadios.size
 

core/data/src/test/java/com/rtbishop/look4sat/core/data/repository/SelectionRepoSearchTest.kt

@@ -156,6 +156,26 @@ class SelectionRepoSearchTest {
         assertEquals(sampleItems.size, repo.getEntriesFlow().first().size)
     }
 
+    @Test
+    fun `virtual type with empty AMSAT list shows empty not everything`() = runTest {
+        // 根因2回归: AMSAT 清单未同步(空)时, 选虚拟类型应显示空列表, 而非全部卫星.
+        val repo = createRepo(items = sampleItems, amSatFm = emptySet())
+        repo.setTypes(listOf("AMSAT Live FM"))
+        assertTrue(repo.getEntriesFlow().first().isEmpty())
+    }
+
+    @Test
+    fun `virtual type combined with regular type unions both lists`() = runTest {
+        val repo = createRepo(
+            items = sampleItems,
+            amSatFm = setOf(25544),
+            amSatLinear = setOf(7530)
+        )
+        repo.setTypes(listOf("AMSAT Live FM", "AMSAT Live Linear"))
+        val results = repo.getEntriesFlow().first()
+        assertEquals(setOf(25544, 7530), results.map { it.catnum }.toSet())
+    }
+
     @Test
     fun `types list has virtual transponder types first and keeps All`() {
         val repo = createRepo(sampleItems)
@@ -192,6 +212,7 @@ private class FakeLocalSourceForSearch(
     override suspend fun insertEntries(entries: List<OrbitalData>) = Unit
     override suspend fun deleteEntries() = Unit
     override suspend fun getIdsWithModes(modes: List<String>): List<Int> = sstvIds
+    override suspend fun getIdsWithModesAndUplink(modes: List<String>): List<Int> = sstvIds
     override suspend fun getRadiosTotal(): Int = 0
     override suspend fun getRadiosWithId(id: Int): List<SatRadio> = emptyList()
     override suspend fun insertRadios(radios: List<SatRadio>, isCustom: Boolean) = Unit

core/domain/src/main/java/com/rtbishop/look4sat/core/domain/repository/ISatelliteRepo.kt

@@ -70,4 +70,9 @@ interface ISatelliteRepo {
      *  Empty modes -> empty result; used to filter the mutual-match satellite
      *  set to transponder satellites (FM voice / linear). */
     suspend fun getSatelliteIdsWithModes(modes: List<String>): List<Int>
+
+    /** Like [getSatelliteIdsWithModes] but only matches records with an uplink
+     *  (real transponders), excluding downlink-only beacons/telemetry that share
+     *  the same mode label. Used by the FM/Linear fallback filter. */
+    suspend fun getSatelliteIdsWithModesAndUplink(modes: List<String>): List<Int>
 }

core/domain/src/main/java/com/rtbishop/look4sat/core/domain/source/ILocalSource.kt

@@ -29,6 +29,7 @@ interface ILocalSource {
     suspend fun insertEntries(entries: List<OrbitalData>)
     suspend fun deleteEntries()
     suspend fun getIdsWithModes(modes: List<String>): List<Int>
+    suspend fun getIdsWithModesAndUplink(modes: List<String>): List<Int>
     suspend fun getRadiosTotal(): Int
     suspend fun getRadiosWithId(id: Int): List<SatRadio>
     suspend fun insertRadios(radios: List<SatRadio>, isCustom: Boolean = false)

core/domain/src/main/java/com/rtbishop/look4sat/core/domain/source/Sources.kt

@@ -62,4 +62,10 @@ object Sources {
         "FM" to "https://www.amsat.org/live-fm-satellites/",
         "Linear" to "https://www.amsat.org/live-linear-satellites/"
     )
+
+    /** Virtual satellite-selection types: transponder/activity filters shown
+     *  at the top of the type picker. They resolve to live lists (AMSAT pages
+     *  or mode=SSTV radios) instead of persisted per-type IDs, and are
+     *  mutually exclusive with the regular TLE-source types in the picker. */
+    val virtualTypeNames = listOf("AMSAT Live FM", "AMSAT Live Linear", "Live SSTV")
 }