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/main/java/com/m57/hermescontrol/ui/system/SystemViewModel.kt

@@ -110,7 +110,7 @@ class SystemViewModel(application: Application) :
     val actionProgress =
         ActionProgressController(
             scope = viewModelScope,
-            onFinished = { loadAll() },
+            onFinished = { status -> onActionFinished(status) },
         )
 
     private var actionPollingJob: Job? = null
@@ -223,6 +223,38 @@ class SystemViewModel(application: Application) :
         }
     }
 
+    /**
+     * Fired when [actionProgress] finishes tracking a backend action. For the
+     * `hermes-update` action we additionally fetch the durable update receipt
+     * (issue #958) and append its summary to the end of the progress popup,
+     * then refresh the screen so the version row reflects the new build. Other
+     * actions just refresh. A 404 / missing receipt is silently skipped — the
+     * popup already shows success from the action status.
+     */
+    private fun onActionFinished(status: ActionStatusResponse?) {
+        if (status?.name == "hermes-update") {
+            viewModelScope.launch {
+                val receipt = fetchUpdateReceiptLines()
+                if (receipt.isNotEmpty()) actionProgress.pushTrailingLines(receipt)
+            }
+        }
+        loadAll()
+    }
+
+    /**
+     * Pull `GET /api/hermes/update/receipt` and render a compact summary block
+     * for the popup. Returns an empty list when the endpoint is unavailable
+     * (old backend, no receipt yet, or any error) so the caller appends nothing.
+     */
+    private suspend fun fetchUpdateReceiptLines(): List<String> {
+        val result =
+            withContext(Dispatchers.IO) {
+                safeApiCall { ApiClient.hermesApi.getUpdateReceipt() }
+            }
+        val data = (result as? NetworkResult.Success)?.data ?: return emptyList()
+        return formatUpdateReceiptLines(data)
+    }
+
     // ── Gateway actions ────────────────────────────────────────────────
 
     fun startGateway() {

app/src/main/java/com/m57/hermescontrol/ui/system/UpdateReceiptFormatting.kt

@@ -0,0 +1,46 @@
+package com.m57.hermescontrol.ui.system
+
+import com.m57.hermescontrol.data.model.UpdateReceipt
+import com.m57.hermescontrol.data.model.UpdateReceiptResponse
+import com.m57.hermescontrol.data.model.UpdateReceiptSummary
+
+/**
+ * Render a compact, popup-friendly summary of an update receipt (issue #958).
+ *
+ * Returns an empty list when there is nothing to show (no receipt, old
+ * backend, or any malformed payload) so callers can skip appending entirely.
+ *
+ * Pure + [internal] so it is unit-testable without mocking the API layer.
+ */
+internal fun formatUpdateReceiptLines(receipt: UpdateReceiptResponse?): List<String> {
+    if (receipt == null) return emptyList()
+    val summary: UpdateReceiptSummary? = receipt.summary
+    val full: UpdateReceipt? = receipt.receipt
+    if (summary == null && full == null) return emptyList()
+
+    val lines = mutableListOf<String>()
+    lines.add("Update receipt")
+
+    val outcome = summary?.outcome ?: full?.outcome
+    if (outcome != null) lines.add("Outcome: $outcome")
+
+    val pre = full?.preUpdate
+    val post = full?.postUpdate
+    if (pre != null || post != null) {
+        val from = pre?.version ?: pre?.sha?.take(8) ?: "?"
+        val to = post?.version ?: post?.sha?.take(8) ?: "?"
+        lines.add("Version: $from → $to")
+    } else if (summary?.postVersion != null) {
+        lines.add("Version: → ${summary.postVersion}")
+    }
+
+    val fleet = full?.fleet
+    if (!fleet.isNullOrEmpty()) {
+        val states = fleet.map { "${it.profile ?: "?"}: ${it.state ?: "?"}" }
+        lines.add("Fleet: ${states.joinToString(", ")}")
+    } else if (summary != null && !summary.fleetStates.isNullOrEmpty()) {
+        lines.add("Fleet: ${summary.fleetStates.joinToString(", ")}")
+    }
+
+    return lines
+}