fix(run-evidence): close SQLite connections in sensors, API and tests

Why

ADR 0053 decision 5 requires Python 3.13 core and package test lanes. On 3.13 a SQLite connection that is never closed raises ResourceWarning: unclosed database when it is garbage-collected. filterwarnings = ["error"] turns that into a failure, and because it happens at garbage collection, a different test fails on each run. On main this affects about 10 core tests per run and tests in phlo-api, phlo-dagster, phlo-dlt, phlo-polaris and phlo-iceberg. This is the first of three PRs before the 3.13 CI lanes.

Production fixes

• _SqlRunEvidenceStore supports with, which calls the existing close().
• phlo_dagster.wap_sensors closes the store from default_run_evidence_store() after it reads quality results and after it reconciles a promoted run. Before this change, each call leaked one SQLite connection.
• _idempotency_connection() in phlo_api.api.operation_controls closes its connection if schema setup raises. All six callers already close it on the normal path.
• The Observatory read-model cache serialises the value before it opens a connection. A value it cannot serialise no longer leaks a connection.

Test fixes

• A new autouse fixture in the root conftest.py tracks every SQLiteRunEvidenceStore and pyiceberg SqlCatalog/InMemoryCatalog a test creates. When the test ends, it closes each store and disposes each catalog engine. This covers about 110 store constructions and the catalog fixtures without editing each call site, including stores that hooks create indirectly.
• Tests that open sqlite3.connect(...) directly now wrap it in closing(...). with sqlite3.connect() alone commits but does not close.
• The WAP sensor tests wrap their injected store in nullcontext so the shared store stays open.

Verification

• Python 3.13.14 with -W error::ResourceWarning:
  • Core: 3420 passed. The one failure, test_ci_test_partition, is the clickhouse-connect 'u' warning in its subprocess, which the next PR fixes.
  • phlo-api 1368, phlo-dagster 545, phlo-iceberg 391 and phlo-polaris 40 passed.
  • A connection tracker found no unclosed run-evidence, catalog or API connections. The one remaining unclosed connection is inside coverage when it reads a deliberately corrupt data file in test_unreadable_coverage_data_blocks, which passes.
• Python 3.12:
  • Core: 3421 passed, and make test-core-regression passed 447.
  • phlo-api, phlo-dagster, phlo-polaris and phlo-iceberg pass unchanged.
  • phlo-dlt fails only test_csv_upload.py::test_candidate_staging_supplies_required_provenance_to_the_real_iceberg_schema, an order-dependent flake that also fails on main. It is tracked separately.
• make check passes.