feat: Session Sovereignty Report Generator (#957)

- Add `src/timmy/sovereignty/session_report.py` with `generate_report()`,
  `commit_report()`, `generate_and_commit_report()`, and `mark_session_start()`
- Add `src/timmy/sovereignty/__init__.py` exporting the public API
- Move `get_session_logger`, `get_sovereignty_store`, and `GRADUATION_TARGETS`
  to module-level imports (graceful fallback on ImportError) so tests can
  patch them at the correct namespace
- Fix broken `patch.object` in test that raised AttributeError on pydantic settings
- Add `pytestmark = pytest.mark.unit` so tests run under `tox -e unit`
- All 23 sovereignty report tests pass

Fixes #957

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/timmy/sovereignty/session_report.py

@@ -28,6 +28,18 @@ import httpx
 
 from config import settings
 
+# Optional module-level imports — degrade gracefully if unavailable at import time
+try:
+    from timmy.session_logger import get_session_logger
+except Exception:  # ImportError or circular import during early startup
+    get_session_logger = None  # type: ignore[assignment]
+
+try:
+    from infrastructure.sovereignty_metrics import GRADUATION_TARGETS, get_sovereignty_store
+except Exception:
+    GRADUATION_TARGETS: dict = {}  # type: ignore[assignment]
+    get_sovereignty_store = None  # type: ignore[assignment]
+
 logger = logging.getLogger(__name__)
 
 # Module-level session start time; set by mark_session_start()
@@ -197,8 +209,8 @@ def _gather_session_data() -> dict[str, Any]:
     }
 
     try:
-        from timmy.session_logger import get_session_logger
-
+        if get_session_logger is None:
+            return default
         sl = get_session_logger()
         sl.flush()
 
@@ -255,8 +267,8 @@ def _gather_sovereignty_data() -> dict[str, Any]:
     - ``previous_session``: most recent prior value for each metric
     """
     try:
-        from infrastructure.sovereignty_metrics import GRADUATION_TARGETS, get_sovereignty_store
-
+        if get_sovereignty_store is None:
+            return {"metrics": {}, "deltas": {}, "previous_session": {}}
         store = get_sovereignty_store()
         summary = store.get_summary()
 
@@ -333,10 +345,6 @@ def _render_markdown(
         lines.append("")
 
     # Sovereignty scorecard
-    try:
-        from infrastructure.sovereignty_metrics import GRADUATION_TARGETS
-    except Exception:
-        GRADUATION_TARGETS = {}
 
     lines += [
         "## Sovereignty Scorecard",

tests/timmy/test_session_report.py

@@ -12,6 +12,8 @@ from unittest.mock import MagicMock, patch
 
 import pytest
 
+pytestmark = pytest.mark.unit
+
 from timmy.sovereignty.session_report import (
     _format_duration,
     _gather_session_data,
@@ -293,9 +295,6 @@ class TestGenerateReport:
 
 class TestCommitReport:
     def test_returns_false_when_gitea_disabled(self):
-        with patch.object(type(settings := __import__("config").settings), "gitea_enabled", False):
-            pass  # mock via config patch instead
-
         with patch("timmy.sovereignty.session_report.settings") as mock_settings:
             mock_settings.gitea_enabled = False
             result = commit_report("# test", "dashboard")