[test] fix: use absolute coverage path in MiniMax-M2 functional test

Use hardcoded /opt/Megatron-Bridge paths for --data-file and --source,
matching the pattern used by the qwen3_moe functional test. The dynamic
tmp_path-based coverage file caused issues when sys.executable resolves
to the container Python rather than the uv-managed venv.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Signed-off-by: yaoyu-33 <yaoyu.094@gmail.com>

Author: yaoyu-33

tests/functional_tests/test_groups/models/minimax_m2/test_minimax_m2_conversion.py

@@ -143,8 +143,7 @@ def test_minimax_m2_conversion_parallelism(self, toy_model_path, tmp_path, tp, p
         test_output_dir = tmp_path / f"minimax_m2_{test_name}"
         test_output_dir.mkdir(exist_ok=True)
 
-        repo_root = Path(__file__).resolve().parents[5]
-        coverage_file = tmp_path / ".coverage"
+        repo_root = "/opt/Megatron-Bridge"
         cmd = [
             sys.executable,
             "-m",
@@ -154,10 +153,10 @@ def test_minimax_m2_conversion_parallelism(self, toy_model_path, tmp_path, tp, p
             "-m",
             "coverage",
             "run",
-            f"--data-file={coverage_file}",
-            f"--source={repo_root}",
+            f"--data-file={repo_root}/.coverage",
+            f"--source={repo_root}/",
             "--parallel-mode",
-            str(repo_root / "examples/conversion/hf_megatron_roundtrip_multi_gpu.py"),
+            f"{repo_root}/examples/conversion/hf_megatron_roundtrip_multi_gpu.py",
             "--hf-model-id",
             toy_model_path,
             "--output-dir",