fix(cli): keep prompt stable and flush stale arrow-key input

tests/test_cli_input_minimal.py

@@ -0,0 +1,37 @@
+import builtins
+
+import nanobot.cli.commands as commands
+
+
+def test_read_interactive_input_uses_plain_input(monkeypatch) -> None:
+    captured: dict[str, object] = {}
+
+    def fake_print(*args, **kwargs):
+        captured["printed"] = args
+        captured["print_kwargs"] = kwargs
+
+    def fake_input(prompt: str = "") -> str:
+        captured["prompt"] = prompt
+        return "hello"
+
+    monkeypatch.setattr(commands.console, "print", fake_print)
+    monkeypatch.setattr(builtins, "input", fake_input)
+
+    value = commands._read_interactive_input()
+
+    assert value == "hello"
+    assert captured["prompt"] == ""
+    assert captured["print_kwargs"] == {"end": ""}
+    assert captured["printed"] == ("[bold blue]You:[/bold blue] ",)
+
+
+def test_flush_pending_tty_input_skips_non_tty(monkeypatch) -> None:
+    class FakeStdin:
+        def fileno(self) -> int:
+            return 0
+
+    monkeypatch.setattr(commands.sys, "stdin", FakeStdin())
+    monkeypatch.setattr(commands.os, "isatty", lambda _fd: False)
+
+    commands._flush_pending_tty_input()
+