feat(agents): 新增 mydsh 启动器 —— DeepSeek Harness CLI 包装

- launcher _BACKENDS 加 dsh：profile 透传、zstd 会话列表（session/title 或首条用户消息）、
  --resume 透传、DSH_HOME 环境变量与 expanduser
- entrypoints/cli/completion/打包/卸载全触点 + TestDsh 用例（裸跑/版本/透传/列表/缺 bin）

tests/test_entrypoints.py

@@ -9,6 +9,7 @@ from myagents.entrypoints import (
     claude_cli,
     codex_cli,
     cursor_cli,
+    dsh_cli,
     hermes_cli,
     kimi_cli,
 )
@@ -204,6 +205,49 @@ class TestMycursorEntrypoint:
             assert mock_run.call_args[0][0][-2:] == ["--resume", "abc123"]
 
 
+class TestMydshEntrypoint:
+    """``mydsh`` standalone entrypoint."""
+
+    def test_runs_dsh(self) -> None:
+        runner = CliRunner()
+        with (
+            patch("myagents.launcher.shutil.which", return_value="/usr/bin/dsh"),
+            patch("myagents.launcher.subprocess.run") as mock_run,
+        ):
+            mock_run.return_value = MagicMock(returncode=0)
+            result = runner.invoke(dsh_cli, [])
+            assert result.exit_code == 0
+            # dsh is a profile launcher; no default args are injected.
+            assert mock_run.call_args[0][0] == ["/usr/bin/dsh"]
+
+    def test_version_shows_mydsh(self) -> None:
+        runner = CliRunner()
+        result = runner.invoke(dsh_cli, ["--version"])
+        assert result.exit_code == 0
+        assert "mydsh" in result.output
+
+    def test_passthrough(self, tmp_path: Path) -> None:
+        """``--resume <id>`` passes through to the native dsh CLI."""
+        runner = CliRunner()
+        with (
+            patch("myagents.launcher.shutil.which", return_value="/usr/bin/dsh"),
+            patch("myagents.launcher.subprocess.run") as mock_run,
+        ):
+            mock_run.return_value = MagicMock(returncode=0)
+            result = runner.invoke(
+                dsh_cli, ["--cwd", str(tmp_path), "--resume", "abc123"]
+            )
+            assert result.exit_code == 0
+            assert mock_run.call_args[0][0][-2:] == ["--resume", "abc123"]
+
+    def test_missing_binary_exits_127(self) -> None:
+        runner = CliRunner()
+        with patch("myagents.launcher.shutil.which", return_value=None):
+            result = runner.invoke(dsh_cli, [])
+            assert result.exit_code == 127
+            assert "dsh CLI not found" in result.output
+
+
 class TestTmuxOption:
     """``--tmux`` / ``-t`` wraps the backend in an attachable tmux session."""