security(#21): gate scale PASS evidence on cleanup

[rblake2320]

Summary

• publish each portable PASS rung only after owned process-tree and launcher cleanup completes
• fail closed on incomplete cleanup or malformed cleanup receipts, leaving no finalized rung or manifest
• emit strict cleanup-control receipts bound to each portable rung SHA-256 without changing the pinned ecosystem consumer schema
• separately attest and upload the cleanup-control archive

Tracks #21. This PR closes a mechanism/evidence-ordering gap; it does not complete the live 10/15/20 evidence run.

Verification

• python -m pytest tests/test_restricted_scale_producer.py -q - 42 passed
• python -m pytest tests/ -q - 824 passed, 10 skipped
• python -m ruff check experiments/fabric_v2/restricted_scale_producer.py tests/test_restricted_scale_producer.py - passed
• python -m compileall -q experiments/fabric_v2/restricted_scale_producer.py - passed
• python tools/release_gate.py audit --root . - 45 passed, 0 failed
• python test_self_connect.py - 72/72 passed
• workflow YAML parsed successfully

Boundaries

No provider, model, or live restricted runner was dispatched. The cleanup-control artifact proves only producer-owned process cleanup for a successful rung. It does not prove runner ephemerality, credential availability, completed 10/15/20 execution, consumer acceptance, or partner/government readiness. Issue #21 remains open until the live evidence and independent review gates complete. Issue #3 remains owner-credential and managed-policy deployment gated; this PR does not create fake signing evidence.