test: remediate and stabilize auxiliary backend and frontend tests

- Standardized task log, LLM provider, and report profile tests.
- Relocated auxiliary tests into __tests__ directories for consistency.
- Updated git_service and defensive guards with minor stability fixes discovered during testing.
- Added UX integration tests for the reports list component.

backend/src/core/task_manager/__tests__/test_task_logger.py

@@ -0,0 +1,102 @@
+# [DEF:__tests__/test_task_logger:Module]
+# @RELATION: VERIFIES -> ../task_logger.py
+# @PURPOSE: Contract testing for TaskLogger
+# [/DEF:__tests__/test_task_logger:Module]
+
+import pytest
+from unittest.mock import MagicMock
+from src.core.task_manager.task_logger import TaskLogger
+
+# @TEST_FIXTURE: valid_task_logger -> {"task_id": "test_123", "add_log_fn": lambda *args: None, "source": "test_plugin"}
+@pytest.fixture
+def mock_add_log():
+    return MagicMock()
+
+@pytest.fixture
+def task_logger(mock_add_log):
+    return TaskLogger(task_id="test_123", add_log_fn=mock_add_log, source="test_plugin")
+
+# @TEST_CONTRACT: TaskLoggerModel -> Invariants
+def test_task_logger_initialization(task_logger):
+    """Verify TaskLogger is bound to specific task_id and source."""
+    assert task_logger._task_id == "test_123"
+    assert task_logger._default_source == "test_plugin"
+
+# @TEST_CONTRACT: invariants -> "All specific log methods (info, error) delegate to _log"
+def test_log_methods_delegation(task_logger, mock_add_log):
+    """Verify info, error, warning, debug delegate to internal _log."""
+    task_logger.info("info message", metadata={"k": "v"})
+    mock_add_log.assert_called_with(
+        task_id="test_123",
+        level="INFO",
+        message="info message",
+        source="test_plugin",
+        metadata={"k": "v"}
+    )
+    
+    task_logger.error("error message", source="override")
+    mock_add_log.assert_called_with(
+        task_id="test_123",
+        level="ERROR",
+        message="error message",
+        source="override",
+        metadata=None
+    )
+
+    task_logger.warning("warning message")
+    mock_add_log.assert_called_with(
+        task_id="test_123",
+        level="WARNING",
+        message="warning message",
+        source="test_plugin",
+        metadata=None
+    )
+
+    task_logger.debug("debug message")
+    mock_add_log.assert_called_with(
+        task_id="test_123",
+        level="DEBUG",
+        message="debug message",
+        source="test_plugin",
+        metadata=None
+    )
+
+# @TEST_CONTRACT: invariants -> "with_source creates a new logger with the same task_id"
+def test_with_source(task_logger):
+    """Verify with_source returns a new instance with updated default source."""
+    new_logger = task_logger.with_source("new_source")
+    assert isinstance(new_logger, TaskLogger)
+    assert new_logger._task_id == "test_123"
+    assert new_logger._default_source == "new_source"
+    assert new_logger is not task_logger
+
+# @TEST_EDGE: missing_task_id -> raises TypeError
+def test_missing_task_id():
+    with pytest.raises(TypeError):
+        TaskLogger(add_log_fn=lambda x: x)
+
+# @TEST_EDGE: invalid_add_log_fn -> raises TypeError
+# (Python doesn't strictly enforce this at init, but let's verify it fails on call if not callable)
+def test_invalid_add_log_fn():
+    logger = TaskLogger(task_id="msg", add_log_fn=None)
+    with pytest.raises(TypeError):
+        logger.info("test")
+
+# @TEST_INVARIANT: consistent_delegation
+def test_progress_log(task_logger, mock_add_log):
+    """Verify progress method correctly formats metadata."""
+    task_logger.progress("Step 1", 45.5)
+    mock_add_log.assert_called_with(
+        task_id="test_123",
+        level="INFO",
+        message="Step 1",
+        source="test_plugin",
+        metadata={"progress": 45.5}
+    )
+    
+    # Boundary checks
+    task_logger.progress("Step high", 150)
+    assert mock_add_log.call_args[1]["metadata"]["progress"] == 100
+    
+    task_logger.progress("Step low", -10)
+    assert mock_add_log.call_args[1]["metadata"]["progress"] == 0