fix: update tests for unified spawn-per-call execution model

- Docker env tests: verify _build_init_env_args() instead of per-execute
  Popen flags (env forwarding is now init-time only)
- Docker: preserve explicit forward_env bypass of blocklist from main
- Daytona tests: adapt to SDK-native timeout, _ThreadedProcessHandle,
  base.py interrupt handling, HERMES_STDIN_ heredoc prefix
- Modal tests: fix _load_module to include _ThreadedProcessHandle stub,
  check ensurepip in _resolve_modal_image instead of __init__
- SSH tests: mock time.sleep on base module instead of removed ssh import
- Add missing BaseEnvironment attributes to __new__()-based test fixtures

tests/tools/test_ssh_environment.py

@@ -43,7 +43,7 @@ class TestBuildSSHCommand:
                             lambda *a, **k: MagicMock(stdout=iter([]),
                                                       stderr=iter([]),
                                                       stdin=MagicMock()))
-        monkeypatch.setattr("tools.environments.ssh.time.sleep", lambda _: None)
+        monkeypatch.setattr("tools.environments.base.time.sleep", lambda _: None)
 
     def test_base_flags(self):
         env = SSHEnvironment(host="h", user="u")