perf(validation): add reusable checked-hash focused runner

[8Dionysus]

Summary

• Add an opt-in focused-core runner that executes one real pytest.main() in the initializer process.
• Bind a validated external checked-hash bytecode prefix before importing pytest; prime only the selected product core, selected test, and imported sources on a cold run, then reuse source-validated caches.
• Keep pytest assertion rewriting in memory with -B, reject polluted or mismatched inherited prefixes, and preserve the actual pytest status when optional cache priming warns.
• Document the route and register its contract test in the validation lane and evidence graph.

Verification

• python3 -B -m pytest -q -p no:cacheprovider tests/test_pytest_checked_hash_core.py tests/test_session_memory_import_core.py tests/test_session_memory_privacy_core.py tests/test_session_memory_outbox_core.py tests/test_validation_evidence_graph.py tests/test_validation_scheduler_experiment.py — 65 passed.
• python3 scripts/validation_lanes.py --check — passed.
• python3 scripts/generate_decision_indexes.py --check — passed.
• python3 -B scripts/audit_public_tree.py --root . --fail-on blocking — 0 blocking findings.
• Fresh and shared-prefix helper smoke runs passed all three focused cores with checked-hash-only caches and no pytest-rewrite files; cold prime and steady runs were measured separately.

Evidence boundary

This remains an owner-local feedback optimization. It is not CI, merge, deployment, installed-parity, runtime, artifact-trust, or acceptance evidence. Local graph validation requiring the pinned .deps/aoa-sdk checkout was not available in this landing worktree; no dependency or gate was bypassed.