test(mutual): 钉死 fixture 时间基准，消除时段性 flaky

fixture 用 2024-03-09 固定 ISS TLE + System.currentTimeMillis() 起点；SGP4 带阻力衰减 942 天后高度仅 ≈262km，12h 窗口内可能无广州过境 → 3 条依赖过境窗的用例时段性失败（Gradle 缓存 FROM-CACHE 会掩盖上一次的真跑）。

- TestOrbits.FIXTURE_BASE（2024-03-10T00:00Z，历元后约 18h）取代默认 System.currentTimeMillis()

- MutualViewModel 墙钟可注入：nowMillis: () -> Long = System::currentTimeMillis（第 4 个默认参数，生产行为逐位不变；工厂具名构造零改动）

- 断言里的 now 改用同一基准；prefill/scroll 测试不碰时间未动

修后：:feature:mutual 28/28，全量 ./gradlew test 451/451。

feature/mutual/src/main/java/com/rtbishop/look4sat/feature/mutual/MutualViewModel.kt

@@ -82,7 +82,10 @@ class MutualViewModel(
     private val settingsRepo: ISettingsRepo,
     // Injected so unit tests can run the pass computation on a test dispatcher;
     // production callers keep the CPU-bound pool default.
-    private val computeDispatcher: CoroutineDispatcher = Dispatchers.Default
+    private val computeDispatcher: CoroutineDispatcher = Dispatchers.Default,
+    // Injected so unit tests can pin the wall clock to the fixture TLE epoch and
+    // stay deterministic; production callers keep the real clock default.
+    private val nowMillis: () -> Long = System::currentTimeMillis
 ) : ViewModel() {
 
     private val _uiState = MutableStateFlow(MutualUiState())
@@ -303,7 +306,7 @@ class MutualViewModel(
         queryGeneration += 1
 
         viewModelScope.launch {
-            val now = System.currentTimeMillis()
+            val now = nowMillis()
             // 转发器类型筛选: 使用硬编码 AMSAT Live 清单 (见 Sources):
             // FM = {SO-50, ISS ZARYA, AO-123}, Linear = {RS-44, FO-29,
             // AO-7, AO-73, JO-97}. 不再依赖 AMSAT 网页同步: 任何网络下都

feature/mutual/src/test/java/com/rtbishop/look4sat/feature/mutual/MutualViewModelTest.kt

@@ -53,7 +53,9 @@ class MutualViewModelTest {
     ): MutualViewModel = MutualViewModel(
         satelliteRepo = FakeSatelliteRepo(satellites, passes),
         settingsRepo = FakeSettingsRepo(position),
-        computeDispatcher = StandardTestDispatcher(mainDispatcherRule.dispatcher.scheduler)
+        computeDispatcher = StandardTestDispatcher(mainDispatcherRule.dispatcher.scheduler),
+        // Pin the clock to the fixture base so results never depend on wall time.
+        nowMillis = { TestOrbits.FIXTURE_BASE }
     )
 
     private fun TestScope.queryAndSettle(vm: MutualViewModel) {
@@ -219,7 +221,7 @@ class MutualViewModelTest {
         assertTrue(state.mutualPasses.all { it.catNum == 25544 })
         assertTrue(state.mutualPasses.all { it.name == "ISS (ZARYA)" })
         // AOS/LOS within the searched horizon
-        val now = System.currentTimeMillis()
+        val now = TestOrbits.FIXTURE_BASE
         assertTrue(state.mutualPasses.all { it.startTime >= now - 120_000L })
         assertTrue(state.mutualPasses.all { it.endTime <= now + 12 * 3600_000L + 120_000L })
     }

feature/mutual/src/test/java/com/rtbishop/look4sat/feature/mutual/TestOrbits.kt

@@ -48,6 +48,15 @@ object TestOrbits {
         )
     )
 
+    /**
+     * Fixed wall-clock base for every fixture computation: 2024-03-10T00:00Z,
+     * ~18 h after [ISS]'s TLE epoch, so SGP4 propagates an accurate, healthy
+     * orbit. Tests pin the ViewModel clock to this value as well
+     * (MutualViewModel.nowMillis), which makes pass windows deterministic
+     * instead of rotting as the fixture ages against System.currentTimeMillis().
+     */
+    val FIXTURE_BASE: Long = 1710028800000L
+
     /** Guangzhou (default BA7OPF grid OL62/OL63 area). */
     val GUANGZHOU = GeoPos(23.13, 113.26)
 
@@ -85,7 +94,7 @@ object TestOrbits {
     fun findPassWindows(
         sat: OrbitalObject = ISS,
         pos: GeoPos = GUANGZHOU,
-        time: Long = System.currentTimeMillis(),
+        time: Long = FIXTURE_BASE,
         hoursAhead: Int = 12
     ): List<OrbitalPass> {
         if (!sat.willBeSeen(pos)) return emptyList()