fix: detect running Flatpak Steam correctly

Request only application IDs from flatpak ps so running Steam instances match correctly. Fix client selection validation and cover detection with regression tests.

Refs aclist/dztui#478.

tests/test_process_detection.py

@@ -0,0 +1,57 @@
+import unittest
+from unittest.mock import patch
+
+from dzgui.const.constants import (
+    FLATPAK_APPID,
+    FLATPAK_RUN_CMD,
+    FLATPAK_SANDBOX,
+    STEAM_CMD,
+)
+from dzgui.init import proc
+
+
+class TestSteamDetection(unittest.TestCase):
+    def test_flatpak_detection_with_multiple_running_apps(self):
+        def flatpak_output(args, *, text):
+            # Default `flatpak ps` includes instance, PID, app and runtime columns.
+            if args == ["flatpak", "ps", "--columns=application"]:
+                return f"com.spotify.Client\n{FLATPAK_APPID}\n{FLATPAK_APPID}\n"
+            return f"3904921611\t1257689\t{FLATPAK_APPID}\torg.freedesktop.Platform\n"
+
+        with (
+            patch.object(proc, "has_cmd", return_value=True),
+            patch.object(proc.subprocess, "check_output", side_effect=flatpak_output),
+        ):
+            for client in (FLATPAK_RUN_CMD, FLATPAK_SANDBOX):
+                with self.subTest(client=client):
+                    self.assertTrue(proc.is_steam_running(client))
+
+    def test_flatpak_not_running(self):
+        with patch.object(proc, "has_cmd", return_value=True):
+            for output in ("", "com.spotify.Client\n", f"{FLATPAK_APPID}Helper\n"):
+                with (
+                    self.subTest(output=output),
+                    patch.object(proc.subprocess, "check_output", return_value=output),
+                ):
+                    self.assertFalse(proc.is_flatpak_steam_running())
+
+    def test_flatpak_not_installed(self):
+        with (
+            patch.object(proc, "has_cmd", return_value=False),
+            patch.object(proc.subprocess, "check_output") as check_output,
+        ):
+            self.assertFalse(proc.is_flatpak_steam_running())
+            check_output.assert_not_called()
+
+    def test_native_steam(self):
+        with patch.object(proc, "has_cmd", return_value=True):
+            for running in (True, False):
+                with (
+                    self.subTest(running=running),
+                    patch.object(proc, "is_running", return_value=running),
+                ):
+                    self.assertEqual(proc.is_steam_running(STEAM_CMD), running)
+
+    def test_invalid_client(self):
+        with self.assertRaises(TypeError):
+            proc.is_steam_running("invalid-client")