feat(update): surface backend update receipt in action popup (#958) (#964)

Adopt GET /api/hermes/update/receipt and append its summary to the
end of the hermes-update action progress popup after it finishes.
Additive only: existing checkHermesUpdate + connection-retry polling
is untouched. 404 (old backend) is handled gracefully.

- add UpdateReceiptResponse data model matching backend schema
- add getUpdateReceipt() to HermesApiService
- ActionProgressController gains trailingLines + pushTrailingLines
- ActionProgressDialog renders trailingLines after the log
- SystemViewModel fetches receipt on action finish and formats it
- extract pure formatUpdateReceiptLines for mockk-free testing

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

@@ -189,6 +189,36 @@ class ActionProgressControllerTest {
         assertEquals(callsAfterFirstPoll, calls)
     }
 
+    @Test
+    fun `pushTrailingLines appends after the log without touching the phase`() {
+        val controller = controller()
+        coEvery { mockApi.getActionStatus("hermes-update") } returns
+            Response.success(
+                ActionStatusResponse(name = "hermes-update", running = false, exit_code = 0),
+            )
+
+        controller.open()
+        controller.markStarted("hermes-update")
+        tick()
+
+        assertEquals(ActionProgressPhase.SUCCEEDED, controller.state.value.phase)
+        assertTrue(controller.state.value.trailingLines.isEmpty())
+
+        controller.pushTrailingLines(listOf("Outcome: success", "Version: 0.20.4 → 0.20.5"))
+
+        val state = controller.state.value
+        assertEquals(ActionProgressPhase.SUCCEEDED, state.phase)
+        assertEquals(listOf("Outcome: success", "Version: 0.20.4 → 0.20.5"), state.trailingLines)
+    }
+
+    @Test
+    fun `pushTrailingLines ignores empty input`() {
+        val controller = controller()
+        controller.open()
+        controller.pushTrailingLines(emptyList())
+        assertTrue(controller.state.value.trailingLines.isEmpty())
+    }
+
     @Test
     fun `onFinished is not called when dismissed mid-run`() {
         val controller = controller()

app/src/test/java/com/m57/hermescontrol/ui/system/UpdateReceiptFormattingTest.kt

@@ -0,0 +1,109 @@
+package com.m57.hermescontrol.ui.system
+
+import com.m57.hermescontrol.data.model.UpdateReceipt
+import com.m57.hermescontrol.data.model.UpdateReceiptFleetEntry
+import com.m57.hermescontrol.data.model.UpdateReceiptResponse
+import com.m57.hermescontrol.data.model.UpdateReceiptSummary
+import com.m57.hermescontrol.data.model.UpdateReceiptVersion
+import org.junit.Assert.assertEquals
+import org.junit.Assert.assertTrue
+import org.junit.Test
+
+/**
+ * Pure-logic tests for [formatUpdateReceiptLines] (issue #958). Mockk cannot
+ * self-attach its agent in this sandbox, so these avoid the API layer entirely
+ * and exercise the formatting directly.
+ */
+class UpdateReceiptFormattingTest {
+    @Test
+    fun `null receipt yields empty list`() {
+        assertTrue(formatUpdateReceiptLines(null).isEmpty())
+    }
+
+    @Test
+    fun `empty receipt (no summary, no record) yields empty list`() {
+        assertTrue(formatUpdateReceiptLines(UpdateReceiptResponse()).isEmpty())
+    }
+
+    @Test
+    fun `full receipt renders outcome version and fleet`() {
+        val receipt =
+            UpdateReceiptResponse(
+                receipt =
+                    UpdateReceipt(
+                        outcome = "success",
+                        preUpdate = UpdateReceiptVersion(version = "0.20.4", sha = "a".repeat(40)),
+                        postUpdate = UpdateReceiptVersion(version = "0.20.5", sha = "b".repeat(40)),
+                        fleet =
+                            listOf(
+                                UpdateReceiptFleetEntry(profile = "default", state = "current"),
+                                UpdateReceiptFleetEntry(profile = "work", state = "stale"),
+                            ),
+                    ),
+                summary =
+                    UpdateReceiptSummary(
+                        outcome = "success",
+                        postVersion = "0.20.5",
+                        fleetStates = listOf("current", "stale"),
+                    ),
+            )
+
+        val lines = formatUpdateReceiptLines(receipt)
+        assertEquals(
+            listOf(
+                "Update receipt",
+                "Outcome: success",
+                "Version: 0.20.4 → 0.20.5",
+                "Fleet: default: current, work: stale",
+            ),
+            lines,
+        )
+    }
+
+    @Test
+    fun `summary-only receipt falls back to postVersion and fleetStates`() {
+        val receipt =
+            UpdateReceiptResponse(
+                summary =
+                    UpdateReceiptSummary(
+                        outcome = "partial",
+                        postVersion = "0.21.0",
+                        fleetStates = listOf("current"),
+                    ),
+            )
+
+        val lines = formatUpdateReceiptLines(receipt)
+        assertEquals(
+            listOf(
+                "Update receipt",
+                "Outcome: partial",
+                "Version: → 0.21.0",
+                "Fleet: current",
+            ),
+            lines,
+        )
+    }
+
+    @Test
+    fun `version falls back to short sha when version is missing`() {
+        val receipt =
+            UpdateReceiptResponse(
+                receipt =
+                    UpdateReceipt(
+                        outcome = "success",
+                        preUpdate = UpdateReceiptVersion(sha = "abcdef1234567890deadbeef"),
+                        postUpdate = UpdateReceiptVersion(sha = "11112222"),
+                    ),
+            )
+
+        val lines = formatUpdateReceiptLines(receipt)
+        assertEquals(
+            listOf(
+                "Update receipt",
+                "Outcome: success",
+                "Version: abcdef12 → 11112222",
+            ),
+            lines,
+        )
+    }
+}