feat: replace Aider with secure mini-SWE-agent worker

tests/test_git_workspace.py

@@ -0,0 +1,60 @@
+import subprocess
+from dataclasses import replace
+from pathlib import Path
+from unittest.mock import Mock
+
+import pytest
+
+from lai_automation.git import GitWorkspace
+from lai_automation.models import ChangeSummary
+
+
+def test_check_diff_accepts_clean_changed_file(settings, tmp_path: Path) -> None:
+    workspace = GitWorkspace(replace(settings, workspace_root=tmp_path), 1)
+    workspace.path.mkdir(parents=True)
+    (workspace.path / "app.php").write_text("<?php\nreturn true;\n")
+    workspace._git = Mock(
+        side_effect=[
+            subprocess.CompletedProcess([], 0, "", ""),
+            subprocess.CompletedProcess([], 0, "app.php\n", ""),
+        ]
+    )
+
+    workspace.check_diff(ChangeSummary(("app.php",), 2, 0))
+
+    assert workspace._git.call_count == 2
+
+
+def test_check_diff_rejects_trailing_whitespace_in_untracked_file(
+    settings,
+    tmp_path: Path,
+) -> None:
+    workspace = GitWorkspace(replace(settings, workspace_root=tmp_path), 1)
+    workspace.path.mkdir(parents=True)
+    (workspace.path / "app.php").write_text("<?php \n")
+    workspace._git = Mock(
+        side_effect=[
+            subprocess.CompletedProcess([], 0, "", ""),
+            subprocess.CompletedProcess([], 0, "app.php\n", ""),
+        ]
+    )
+
+    with pytest.raises(RuntimeError, match="trailing whitespace"):
+        workspace.check_diff(ChangeSummary(("app.php",), 1, 0))
+
+
+def test_check_diff_ignores_unchanged_whitespace_in_tracked_file(
+    settings,
+    tmp_path: Path,
+) -> None:
+    workspace = GitWorkspace(replace(settings, workspace_root=tmp_path), 1)
+    workspace.path.mkdir(parents=True)
+    (workspace.path / "legacy.php").write_text("<?php \nreturn true;\n")
+    workspace._git = Mock(
+        side_effect=[
+            subprocess.CompletedProcess([], 0, "", ""),
+            subprocess.CompletedProcess([], 0, "", ""),
+        ]
+    )
+
+    workspace.check_diff(ChangeSummary(("legacy.php",), 1, 0))