myclaude -r: 修快速连按方向键被退出 + 隐藏光标 + 退出删除行不留空行

- _read_key 改按需读 CSI 序列（方向键读到终止符即返回），连按 \x1b[B 不再被吞进同一序列误判为 ESC 退出
- picker 全程隐藏光标（\x1b[?25l），退出恢复（\x1b[?25h），末尾不再突兀闪现光标
- 退出改用 Delete Line（\x1b[{n}M）删除块区域，替代逐行清空，不再留下 N 个空行
- tests: 新增快速连按方向键回归测试

tests/test_launcher_sessions.py

@@ -340,3 +340,18 @@ class TestReadKey:
 
     def test_escape(self) -> None:
         assert _read_key_from_bytes(b"\x1b") == "esc"
+
+    def test_rapid_arrows_not_merged(self) -> None:
+        """Back-to-back arrow keys stay distinct (no bleed into one ESC)."""
+        r, w = os.pipe()
+        try:
+            # 4 rapid down presses back-to-back, exactly as the terminal sends them
+            os.write(w, b"\x1b[B" * 4)
+            keys = [L._read_key(r) for _ in range(4)]
+            assert keys == ["down"] * 4
+            # bare ESC still reads as its own key afterwards
+            os.write(w, b"\x1b")
+            assert L._read_key(r) == "esc"
+        finally:
+            os.close(r)
+            os.close(w)