Add comprehensive test suite for MVP-1 Personal Tracker CLI

Implements 72 tests covering:
- Model tests (Project, Session, Note, Change)
- ProjectService tests (create, get, list, ensure structure)
- SessionService tests (active session management)
- FileStorage tests (read/write operations)
- Complete flow tests (init -> start -> note -> stop -> show)
- Note consolidation tests

Uses pytest with tmp_path fixtures for isolated testing.

tests/conftest.py

@@ -0,0 +1,102 @@
+"""Pytest fixtures for tracker tests."""
+
+import json
+import tempfile
+from datetime import datetime, timedelta
+from pathlib import Path
+from typing import Optional
+
+import pytest
+
+from tracker.models import Project, Session, Note, NoteType, Change
+
+
+@pytest.fixture
+def tmp_project_dir(tmp_path):
+    """Create a temporary directory for project tests."""
+    projects_root = tmp_path / "projects"
+    projects_root.mkdir()
+    return projects_root
+
+
+@pytest.fixture
+def sample_project_data():
+    """Sample project data for testing."""
+    return {
+        "id": "test-project-id-123",
+        "name": "Test Project",
+        "slug": "test-project",
+        "description": "A test project for unit testing",
+        "type": "code",
+        "status": "active",
+        "tags": ["python", "testing"],
+        "root_path": "/path/to/projects/test-project",
+        "repo_path": "/path/to/repos/test-project",
+        "created_at": datetime(2024, 1, 15, 10, 0, 0),
+        "updated_at": datetime(2024, 1, 15, 10, 0, 0),
+        "last_session_at": None,
+    }
+
+
+@pytest.fixture
+def sample_project(sample_project_data):
+    """Create a sample Project instance."""
+    return Project(**sample_project_data)
+
+
+@pytest.fixture
+def mock_session(sample_project):
+    """Create a mock session for testing."""
+    return Session(
+        id="session-123",
+        project_slug=sample_project.slug,
+        started_at=datetime(2024, 1, 15, 10, 0, 0),
+        ended_at=datetime(2024, 1, 15, 11, 30, 0),
+        duration_minutes=90,
+        objective="Complete initial implementation",
+        summary="Worked on core features",
+        work_done=["Implemented feature A", "Fixed bug B"],
+        changes=["Added new endpoint"],
+        decisions=["Use JSON for storage"],
+        blockers=[],
+        next_steps=["Add tests", "Write documentation"],
+        references=["https://example.com/docs"],
+        raw_notes=[
+            {"type": "work", "text": "Working on feature A", "timestamp": "2024-01-15T10:15:00"},
+            {"type": "idea", "text": "Consider using caching", "timestamp": "2024-01-15T10:30:00"},
+        ],
+    )
+
+
+@pytest.fixture
+def sample_note():
+    """Create a sample note for testing."""
+    return Note(
+        type=NoteType.WORK,
+        text="Completed the implementation of feature X",
+        created_at=datetime(2024, 1, 15, 10, 30, 0),
+    )
+
+
+@pytest.fixture
+def sample_change():
+    """Create a sample change for testing."""
+    return Change(
+        date=datetime(2024, 1, 15).date(),
+        type="code",
+        title="Added user authentication",
+        impact="Improved security",
+        references=["#123"],
+    )
+
+
+@pytest.fixture
+def tmp_project_with_structure(tmp_project_dir, sample_project_data):
+    """Create a temporary project with directory structure."""
+    slug = sample_project_data["slug"]
+    project_root = tmp_project_dir / slug
+    (project_root / "sessions").mkdir(parents=True)
+    (project_root / "docs").mkdir(parents=True)
+    (project_root / "assets").mkdir(parents=True)
+    (project_root / "meta").mkdir(parents=True)
+    return project_root