Refactor ComfyUI installation script to improve Python environment handling

- Replaced direct calls to `venv/bin/pip` with `python -m pip` to avoid execution errors on network mounts and improve compatibility.
- Introduced a new function `find_comfy_python` to locate the appropriate Python executable for ComfyUI installations.
- Updated the `pip_install_sage` function to utilize the new Python handling, enhancing installation reliability.
- Added tests to verify the new behavior of Python environment detection and installation processes, ensuring robustness.

tests/test_tune_swarm_perf.py

@@ -44,6 +44,7 @@ def test_pip_fail_skips_extra_args(tmp_path, monkeypatch):
     monkeypatch.setattr(mod, "MARKER", data / ".gpu-rent-perf-tuned")
     monkeypatch.setattr(mod, "BACKENDS", backends)
     monkeypatch.setattr(mod, "find_pip", lambda: pip)
+    monkeypatch.setattr(mod, "find_comfy_python", lambda: pip)
     monkeypatch.setattr(mod, "pip_install_sage", lambda _p: False)
 
     assert mod.main() == 0
@@ -79,6 +80,7 @@ def test_pip_ok_patches_extra_args(tmp_path, monkeypatch):
     monkeypatch.setattr(mod, "MARKER", data / ".gpu-rent-perf-tuned")
     monkeypatch.setattr(mod, "BACKENDS", backends)
     monkeypatch.setattr(mod, "find_pip", lambda: pip)
+    monkeypatch.setattr(mod, "find_comfy_python", lambda: pip)
     monkeypatch.setattr(mod, "pip_install_sage", lambda _p: True)
 
     assert mod.main() == 0
@@ -127,9 +129,39 @@ def test_pip_fail_retries_next_run(tmp_path, monkeypatch):
     monkeypatch.setattr(mod, "MARKER", marker)
     monkeypatch.setattr(mod, "BACKENDS", backends)
     monkeypatch.setattr(mod, "find_pip", lambda: pip)
+    monkeypatch.setattr(mod, "find_comfy_python", lambda: pip)
     monkeypatch.setattr(mod, "pip_install_sage", lambda _p: True)
 
     assert mod.main() == 0
     new_m = json.loads(marker.read_text(encoding="utf-8"))
     assert new_m["pip_ok"] is True
     assert "--use-sage-attention" in backends.read_text(encoding="utf-8")
+
+
+def test_pip_install_uses_python_dash_m(tmp_path, monkeypatch):
+    mod = _load()
+    py = tmp_path / "python"
+    py.write_text("", encoding="utf-8")
+    seen: list[list[str]] = []
+
+    def fake_call(cmd, env=None):
+        seen.append(list(cmd))
+        return 0
+
+    monkeypatch.setattr(mod, "sage_already_importable", lambda _p: False)
+    monkeypatch.setattr(mod.subprocess, "check_call", fake_call)
+    assert mod.pip_install_sage(py) is True
+    assert seen and seen[0][:4] == [str(py), "-m", "pip", "install"]
+
+
+def test_pip_install_oserror_returns_false(tmp_path, monkeypatch):
+    mod = _load()
+    py = tmp_path / "python"
+    py.write_text("", encoding="utf-8")
+
+    def boom(*_a, **_k):
+        raise OSError(8, "Exec format error", str(py))
+
+    monkeypatch.setattr(mod, "sage_already_importable", lambda _p: False)
+    monkeypatch.setattr(mod.subprocess, "check_call", boom)
+    assert mod.pip_install_sage(py) is False