feat(ws): consume gateway change events (issue #784) (#837)

* feat(ws): consume gateway change events (cron/sessions/platforms/pairing) for targeted refresh (issue #784)

* test(chat): complete catch-all request stub — kill frozen-collector capture race (slash-focus flake, 4645a2b CI)

---------

Co-authored-by: M57 <hy4ri@users.noreply.github.com>

app/src/test/java/com/m57/hermescontrol/ui/common/RefreshOnChangeTest.kt

@@ -0,0 +1,77 @@
+package com.m57.hermescontrol.ui.common
+
+import androidx.lifecycle.ViewModel
+import com.m57.hermescontrol.data.remote.NetworkResult
+import com.m57.hermescontrol.data.ws.ChangeEventHub
+import com.m57.hermescontrol.data.ws.ChangeEvents
+import com.m57.hermescontrol.data.ws.WsEvent
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.ExperimentalCoroutinesApi
+import kotlinx.coroutines.flow.MutableStateFlow
+import kotlinx.coroutines.test.StandardTestDispatcher
+import kotlinx.coroutines.test.advanceUntilIdle
+import kotlinx.coroutines.test.resetMain
+import kotlinx.coroutines.test.runTest
+import kotlinx.coroutines.test.setMain
+import org.junit.After
+import org.junit.Assert.assertEquals
+import org.junit.Before
+import org.junit.Test
+
+/**
+ * Regression guard for issue #784: `refreshOnChange` must react to hub events
+ * WITHOUT touching the HermesWsClient singleton — constructing a ViewModel
+ * that wires it must be safe in a plain unit-test JVM (no mockkObject of
+ * HermesWsClient, no static mocks). This used to poison the whole suite with
+ * ExceptionInInitializerError at MockKStub.kt:106.
+ */
+@OptIn(ExperimentalCoroutinesApi::class)
+class RefreshOnChangeTest {
+    private val testDispatcher = StandardTestDispatcher()
+
+    private class TestViewModel : ViewModel() {
+        val state = MutableStateFlow("initial")
+
+        init {
+            refreshOnChange(
+                eventType = ChangeEvents.CRON,
+                apiCall = { NetworkResult.Success("refreshed") },
+                onSuccess = { state.value = it },
+            )
+        }
+    }
+
+    @Before
+    fun setUp() {
+        Dispatchers.setMain(testDispatcher)
+    }
+
+    @After
+    fun tearDown() {
+        Dispatchers.resetMain()
+    }
+
+    @Test
+    fun testRefreshOnChange_updatesOnMatchingEvent() =
+        runTest(testDispatcher) {
+            val viewModel = TestViewModel()
+            // Let the init coroutine run so the collector actually subscribes
+            // before the event fires (replay=0 — events before subscription
+            // are dropped, matching production where VMs subscribe at
+            // construction and events arrive afterwards).
+            advanceUntilIdle()
+            ChangeEventHub.emit(WsEvent.ChangeEvent(ChangeEvents.CRON))
+            advanceUntilIdle()
+            assertEquals("refreshed", viewModel.state.value)
+        }
+
+    @Test
+    fun testRefreshOnChange_ignoresOtherEventTypes() =
+        runTest(testDispatcher) {
+            val viewModel = TestViewModel()
+            advanceUntilIdle()
+            ChangeEventHub.emit(WsEvent.ChangeEvent(ChangeEvents.SESSIONS))
+            advanceUntilIdle()
+            assertEquals("initial", viewModel.state.value)
+        }
+}