test(e2e): add minimal startup E2E tests

Add E2E tests for LangBot startup flow:
- tests/e2e/utils/config_factory.py: minimal config generation
- tests/e2e/utils/process_manager.py: LangBot subprocess management
- tests/e2e/conftest.py: E2E fixtures (session-scoped process)
- tests/e2e/test_startup.py: 12 tests for startup verification

Tests verify:
- boot.py + stages execution
- database initialization (SQLite)
- API availability
- migrations applied

Uses embedded databases (SQLite, Chroma) - no external dependencies.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

tests/e2e/conftest.py

@@ -0,0 +1,102 @@
+"""E2E test fixtures.
+
+Provides fixtures for starting real LangBot process with minimal configuration.
+"""
+
+from __future__ import annotations
+
+import pytest
+import tempfile
+import shutil
+import logging
+from pathlib import Path
+
+from tests.e2e.utils.config_factory import create_minimal_config, create_test_directories
+from tests.e2e.utils.process_manager import LangBotProcess, find_project_root
+
+logger = logging.getLogger(__name__)
+
+pytestmark = pytest.mark.e2e
+
+
+@pytest.fixture(scope='session')
+def e2e_port():
+    """Port for E2E testing (non-default to avoid conflicts)."""
+    return 15300
+
+
+@pytest.fixture(scope='session')
+def e2e_tmpdir():
+    """Create temporary directory for E2E testing."""
+    tmpdir = Path(tempfile.mkdtemp(prefix='langbot_e2e_'))
+    logger.info(f'E2E tmpdir: {tmpdir}')
+
+    yield tmpdir
+
+    # Cleanup
+    logger.info(f'Cleaning up E2E tmpdir: {tmpdir}')
+    shutil.rmtree(tmpdir, ignore_errors=True)
+
+
+@pytest.fixture(scope='session')
+def e2e_config_path(e2e_tmpdir, e2e_port):
+    """Create minimal config.yaml for E2E testing."""
+    config_path = create_minimal_config(e2e_tmpdir, port=e2e_port)
+    create_test_directories(e2e_tmpdir)
+    logger.info(f'E2E config: {config_path}')
+    return config_path
+
+
+@pytest.fixture(scope='session')
+def langbot_process(e2e_config_path, e2e_port, e2e_tmpdir):
+    """Start real LangBot process for E2E testing.
+
+    This fixture starts LangBot once per session and reuses it for all tests.
+    Coverage data is collected from the subprocess.
+    """
+    project_root = find_project_root()
+    collect_coverage = True
+
+    proc = LangBotProcess(
+        project_root=project_root,
+        work_dir=e2e_tmpdir,  # Run in tmpdir where data/config.yaml exists
+        port=e2e_port,
+        timeout=60,  # Longer timeout for first startup
+        collect_coverage=collect_coverage,
+    )
+
+    success = proc.start()
+    if not success:
+        stdout, stderr = proc.get_logs()
+        pytest.fail(f'LangBot failed to start:\nstdout: {stdout}\nstderr: {stderr}')
+
+    yield proc
+
+    # Cleanup
+    proc.stop()
+
+    # Combine coverage data if collected
+    if collect_coverage and proc.get_coverage_file():
+        coverage_file = proc.get_coverage_file()
+        if coverage_file.exists():
+            # Copy coverage data to project root for combining
+            target = project_root / '.coverage.e2e'
+            shutil.copy(coverage_file, target)
+            logger.info(f'Coverage data saved to: {target}')
+
+
+@pytest.fixture
+def e2e_client(e2e_port, langbot_process):
+    """HTTP client for E2E testing."""
+    import httpx
+
+    base_url = f'http://127.0.0.1:{e2e_port}'
+
+    with httpx.Client(base_url=base_url, timeout=10.0) as client:
+        yield client
+
+
+@pytest.fixture(scope='session')
+def e2e_db_path(e2e_tmpdir):
+    """Path to SQLite database file."""
+    return e2e_tmpdir / 'data' / 'langbot.db'