fix(indexing): install runtime in worker CLI

[earayu]

Summary

Hotfix for split-process graph indexing failures:

• install worker-side IndexingRuntime in python -m aperag.cli.indexing_worker after queue/quota/metrics/ProductionWorkerFactory are constructed
• wire cleanup_worker_factory=worker_factory.build_for_cleanup_row in the worker runtime, while keeping API cleanup_worker_factory=None
• clear the process-local runtime on worker shutdown via set_runtime(None)
• add regression coverage that the CLI-equivalent runtime install lets graph worker factory resolve DocumentIndex.tenant_scope_key instead of raising IndexingRuntime is not installed (lifespan never ran)

Boundary

This does not move heavy worker logic back into the API process. API-side hard-cut tests remain unchanged and passing.

Verification

• uv run pytest tests/unit_test/indexing/test_worker_runtime_install.py tests/unit_test/test_app_lifespan_no_workers.py tests/boundaries/test_worker_di_parity.py
• uv run ruff check aperag/cli/indexing_worker.py tests/unit_test/indexing/test_worker_runtime_install.py
• uv run ruff format --check aperag/cli/indexing_worker.py tests/unit_test/indexing/test_worker_runtime_install.py