Implemented invocation-level failure diagnostics

tests/test_new_launcher.py

@@ -1,6 +1,7 @@
 import os
 import shutil
 import subprocess
+import sys
 from pathlib import Path
 
 import pytest
@@ -29,3 +30,46 @@ def test_root_launcher_help_smoke():
 
     assert result.returncode == 0
     assert result.stdout.startswith("usage: audita ")
+
+
+def test_root_launcher_writes_error_log_when_uv_is_missing(tmp_path):
+    work_dir = tmp_path / "work"
+    result = subprocess.run(
+        [sys.executable, str(LAUNCHER), "process", "transcript.json", "--glossary", "glossary.yaml", "--work-dir", str(work_dir)],
+        cwd=ROOT,
+        text=True,
+        capture_output=True,
+        env={**os.environ, "PATH": ""},
+        check=False,
+    )
+
+    assert result.returncode == 1
+    assert result.stdout == ""
+    assert "audita: error: uv is required to run this launcher" in result.stderr
+    run_dir = next(work_dir.iterdir())
+    assert f"audita: run directory: {run_dir}" in result.stderr
+    assert (run_dir / "error.log").exists()
+
+
+def test_root_launcher_preserves_child_exit_code_and_writes_fallback_error_log(tmp_path):
+    work_dir = tmp_path / "work"
+    fake_bin = tmp_path / "bin"
+    fake_bin.mkdir()
+    fake_uv = fake_bin / "uv"
+    fake_uv.write_text("#!/bin/sh\nexit 120\n", encoding="utf-8")
+    fake_uv.chmod(0o755)
+
+    result = subprocess.run(
+        [sys.executable, str(LAUNCHER), "process", "transcript.json", "--glossary", "glossary.yaml", "--work-dir", str(work_dir)],
+        cwd=ROOT,
+        text=True,
+        capture_output=True,
+        env={**os.environ, "PATH": str(fake_bin)},
+        check=False,
+    )
+
+    assert result.returncode == 120
+    assert result.stdout == ""
+    assert "audita: subprocess exited with status 120" in result.stderr
+    run_dir = next(work_dir.iterdir())
+    assert (run_dir / "error.log").exists()