Session Order Adjustment

Nucleic-Session: 19C20841-87D4-45F9-A5AD-EBB92B735F82
Co-authored-by: Nucleic <[email protected]>

NucleicRemote/NucleicRemote/Models/RemoteStore.swift

@@ -1242,6 +1242,13 @@ extension DashboardSnapshot {
 }
 
 extension WireSessionSummary {
+    /// Recency key for ordering session lists: the last *user* message, falling back to `updatedAt`
+    /// for sessions with no user message yet (or summaries from a host that predates the field).
+    /// Ordering on this keeps a chat's position steady until the user speaks again, rather than
+    /// reshuffling the list on every bit of agent activity (which bumps `updatedAt` every few
+    /// seconds). Mirrors the Mac sidebar's last-turn ordering.
+    var lastTurnAt: Date { lastUserMessageAt ?? updatedAt }
+
     /// A copy with selected fields overridden — the demo simulator's only way to "mutate" a
     /// summary, whose stored properties are all `let`. Nullable fields use a double optional so a
     /// caller can distinguish "keep" (omit) from "set to nil" (`.some(nil)`). `updatedAt` bumps