Fix retry crash for unregistered remotes in the Sessions popup

Opening a window whose target was removed from the registry (its tab
stays open by design) and failing landed in the action menu with a
"重试连接" row that indexed self.entries directly and raised KeyError,
killing the popup with a traceback.

Only offer the retry action for registered targets, degrade a stale
retry row to a message, and keep the popup alive when a handler raises
anything unexpected instead of dying with a traceback.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

tests/test_selector.py

@@ -1000,5 +1000,50 @@ class SelectorActionTests(unittest.TestCase):
                     os.waitpid(pid, 0)
 
 
+class SelectorRobustnessTests(unittest.TestCase):
+    def test_retry_is_not_offered_for_unregistered_remote_and_never_crashes(self) -> None:
+        with tempfile.TemporaryDirectory() as directory:
+
+            def activate(result: SelectorResult) -> None:
+                raise RuntimeError("ssh: connect to host orangepi port 22: No route to host")
+
+            # The registry is empty: this window's target was removed via
+            # "移除远端记录" while its tab stayed open.
+            window = CatalogWindow(
+                "@7",
+                "remote:orangepi:default",
+                "R orangepi/default",
+                True,
+                False,
+                kind="remote",
+                target="orangepi",
+                session="default",
+                default_label="R orangepi/default",
+            )
+            selector = SessionSelector(
+                [window],
+                RemoteRegistry(Path(directory) / "remotes.json"),
+                "/missing/ssh",
+                activate_handler=activate,
+            )
+            self.addCleanup(selector.pool.close)
+            row = next(
+                item
+                for item in selector._rows()  # type: ignore[attr-defined]
+                if item.key == "window:@7"
+            )
+            self.assertIsNone(selector._activate(row))  # type: ignore[attr-defined]
+            self.assertEqual(selector.view, "actions")
+            kinds = [item.kind for item in selector._rows()]  # type: ignore[attr-defined]
+            self.assertIn("action-window", kinds)
+            self.assertNotIn("action-retry", kinds)
+
+            # A stale retry row must degrade to a message instead of a KeyError.
+            stale = PickerRow("retry:orangepi", "retry", "! orangepi", target="orangepi")
+            self.assertIsNone(selector._activate(stale))  # type: ignore[attr-defined]
+            self.assertEqual(selector.view, "main")
+            self.assertIn("未登记", selector.message)
+
+
 if __name__ == "__main__":
     unittest.main()