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/data/model/UpdateReceiptResponse.kt

@@ -0,0 +1,81 @@
+package com.m57.hermescontrol.data.model
+
+import kotlinx.serialization.Serializable
+
+/**
+ * Durable record of the most recent `hermes update` run, returned by
+ * `GET /api/hermes/update/receipt` (hermes-agent #91277). This is the
+ * authoritative outcome — it survives gateway restarts and log rotation,
+ * unlike heuristic connection-retry polling.
+ *
+ * All fields are nullable: the backend may emit a partial receipt, and the
+ * response is decoded with `ignoreUnknownKeys = true`, so future additions
+ * won't break parsing.
+ *
+ * The same data is also attached (flattened) to
+ * `GET /api/actions/hermes-update/status` under a `receipt` key.
+ */
+@Serializable
+data class UpdateReceiptResponse(
+    val receipt: UpdateReceipt? = null,
+    val summary: UpdateReceiptSummary? = null,
+)
+
+@Serializable
+data class UpdateReceipt(
+    val schema: Int? = null,
+    val startedAt: String? = null,
+    val finishedAt: String? = null,
+    val argv: List<String>? = null,
+    val pid: Int? = null,
+    /** `success` | `partial` | `running`. `running` means the update is still mid-flight. */
+    val outcome: String? = null,
+    val preUpdate: UpdateReceiptVersion? = null,
+    val postUpdate: UpdateReceiptVersion? = null,
+    val steps: List<UpdateReceiptStep>? = null,
+    val skips: List<String>? = null,
+    val gatewayRestart: UpdateReceiptGatewayRestart? = null,
+    val fleet: List<UpdateReceiptFleetEntry>? = null,
+)
+
+@Serializable
+data class UpdateReceiptVersion(
+    val sha: String? = null,
+    val version: String? = null,
+)
+
+@Serializable
+data class UpdateReceiptStep(
+    val name: String? = null,
+    val ok: Boolean? = null,
+    val detail: String? = null,
+    val at: String? = null,
+)
+
+@Serializable
+data class UpdateReceiptGatewayRestart(
+    val at: String? = null,
+    val ok: Boolean? = null,
+)
+
+@Serializable
+data class UpdateReceiptFleetEntry(
+    val profile: String? = null,
+    val pid: Int? = null,
+    val codeSha: String? = null,
+    val state: String? = null,
+)
+
+/**
+ * Flattened highlights of [UpdateReceipt], returned alongside it by the
+ * endpoint. Mirrors the backend's `summary` object so the popup can show the
+ * essentials without walking the full receipt.
+ */
+@Serializable
+data class UpdateReceiptSummary(
+    val outcome: String? = null,
+    val preSha: String? = null,
+    val postSha: String? = null,
+    val postVersion: String? = null,
+    val fleetStates: List<String>? = null,
+)