The device list was rendering its own source code

`"Registered ${'$'}{fmt.format(instant)}"` — `${'$'}` emits a LITERAL dollar
sign, so the template was never evaluated and every device row read

    Registered ${fmt.format(instant)}

Kotlin cannot warn about this: escaping a dollar is a legitimate thing to want,
just never here. And nothing could test it, because the string was assembled
inline inside a `Text(...)`.

Lifted into `registeredLine` so it can be asserted, with a test that fails if
template source ever reaches the screen again. That is the real fix — the
one-character correction would have left the next one just as invisible.

engine 155, client 96, app 35.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

app/src/main/kotlin/io/flamenet/messenger/app/ChatScreens.kt

@@ -2565,15 +2565,7 @@ fun RegisteredDevicesSection(
                         }
                     }
                     Text(
-                        device.createdAt?.let { raw ->
-                            runCatching {
-                                val instant = java.time.Instant.parse(raw)
-                                val fmt = java.time.format.DateTimeFormatter
-                                    .ofPattern("MMM d, yyyy HH:mm")
-                                    .withZone(java.time.ZoneId.systemDefault())
-                                "Registered ${'$'}{fmt.format(instant)}"
-                            }.getOrDefault("Registered $raw")
-                        } ?: "Registered date unknown",
+                        registeredLine(device.createdAt),
                         fontSize = 12.sp,
                         color = Palette.SecondaryText,
                     )
@@ -2671,3 +2663,26 @@ private val DISAPPEAR_LABELS = mapOf(
     86_400 to "a day",
     604_800 to "a week",
 )
+
+/**
+ * "Registered <date>" for one device row.
+ *
+ * 🔴 **This shipped rendering its own source code.** The string was written
+ * `"Registered ${'$'}{fmt.format(instant)}"`, and `${'$'}` emits a LITERAL
+ * dollar sign — so the template was never evaluated and the screen showed
+ * `Registered ${fmt.format(instant)}` to the user. Kotlin cannot warn about
+ * it: escaping a dollar is a legitimate thing to want, just never here.
+ *
+ * Lifted out of the Composable so it can be asserted. A string built inline in
+ * a `Text(...)` is a string nothing can test, which is why this survived.
+ */
+internal fun registeredLine(createdAt: String?): String {
+    val raw = createdAt ?: return "Registered date unknown"
+    return runCatching {
+        val instant = java.time.Instant.parse(raw)
+        val fmt = java.time.format.DateTimeFormatter
+            .ofPattern("MMM d, yyyy HH:mm")
+            .withZone(java.time.ZoneId.systemDefault())
+        "Registered ${fmt.format(instant)}"
+    }.getOrDefault("Registered $raw")
+}