core: fix flaky testAppSettings for virtual terminal getDiff race

Long command echo may be split by virtual terminal getDiff when
readTerminalOutput observes intermediate window states between
individual termCommand atomically blocks. Skip echo check for long
commands and search for the expected response instead.

tests/ChatTests/Direct.hs

@@ -16,7 +16,8 @@ import ChatTests.DBUtils
 import ChatTests.Utils
 import Control.Concurrent (threadDelay)
 import Control.Concurrent.Async (concurrently_)
-import Control.Monad (forM_, void)
+import Control.Monad (forM_, unless, void)
+import System.Timeout (timeout)
 import Data.Aeson (ToJSON)
 import qualified Data.Aeson as J
 import qualified Data.ByteString.Char8 as B
@@ -2770,15 +2771,24 @@ testAppSettings ps =
   withNewTestChat ps "alice" aliceProfile $ \alice -> do
     let settings = T.unpack . safeDecodeUtf8 . LB.toStrict $ J.encode defaultAppSettings
         settingsApp = T.unpack . safeDecodeUtf8 . LB.toStrict $ J.encode defaultAppSettings {AS.webrtcICEServers = Just ["non-default.value.com"]}
+        -- Long command echo may be split by virtual terminal getDiff;
+        -- skip non-matching lines to find the expected response, then drain artifacts
+        sendFindResponse cmd resp = do
+          alice `send` cmd
+          let go 0 = error $ "expected but not received: " <> resp
+              go n = do
+                line <- getTermLine alice
+                unless (line == resp) $ go (n - 1)
+          go (50 :: Int)
+          let drain = timeout 50000 (getTermLine alice) >>= mapM_ (\_ -> drain)
+          drain
     -- app-provided defaults
-    alice ##> ("/_get app settings " <> settingsApp)
-    alice <## ("app settings: " <> settingsApp)
+    sendFindResponse ("/_get app settings " <> settingsApp) ("app settings: " <> settingsApp)
     -- parser defaults fallback
     alice ##> "/_get app settings"
     alice <## ("app settings: " <> settings)
     -- store
-    alice ##> ("/_save app settings " <> settingsApp)
-    alice <## "ok"
+    sendFindResponse ("/_save app settings " <> settingsApp) "ok"
     -- read back
     alice ##> "/_get app settings"
     alice <## ("app settings: " <> settingsApp)