[codex] Require cache suppression for Python tasks

[Jordak]

Summary

• Require Python task bundles to suppress ordinary Python/pytest cache byproducts with PYTHONDONTWRITEBYTECODE=1 and PYTEST_ADDOPTS=-p no:cacheprovider.
• Add that environment to current Python task bundles and refresh generated task cards/reference artifacts.
• Add task-bundle validation so future Python tasks fail validation if the cache-suppression env is omitted.
• Close sqlite connections explicitly in Codex metadata helpers/readers to remove Python 3.13 ResourceWarning stderr leakage in unit tests.

Why

Previously, the Click edit-scope smoke could fail despite passing behavioral graders because normal agent self-checks created .pytest_cache/ and __pycache__/ files, which polluted changed-file scope scoring. That should not remain as-is because the task is meant to measure intentional edit scope, not ordinary verification residue.

With this PR, Python tasks suppress those cache byproducts through task-local environment, and validation prevents future Python tasks from forgetting the setting.

Readiness evidence: follow-up from issue #100 / Click edit-scope smoke trial cache failures.
Readiness verdict: Ready to Implement

Validation

• PYENV_VERSION=3.13.5 python3 -m agentlab task validate --check-task-cards tasks
• PYENV_VERSION=3.13.5 python3 -m agentlab task verify-reference for 8 Python task bundles with reference artifacts
• PYENV_VERSION=3.13.5 python3 -m unittest tests.test_task_bundle_integrity tests.test_cli tests.test_task_cards tests.test_review_proposals
• PYENV_VERSION=3.13.5 python3 -m unittest
• git diff --check

Smoke Trials

All four Click default_map edit-scope smoke trials passed with exactly src/click/core.py and tests/test_defaults.py changed and no score notes:

• Codex low: passed
• Codex xhigh: passed
• Claude Haiku (claude-haiku-4-5-20251001): passed
• Claude Opus (opus, resolved to claude-opus-4-8): passed

Local run directory: runs/click-default-map-edit-scope-cachefix-2026-06-08/