fix(execution): prevent concurrent runners from submitting twice

[Pigbibi]

Summary

• Bind live state access and a native Firestore create/owner-checked delete transaction to the same resolved backend; claim before state and market reads.
• Retain ownership for uncertain or partial execution and failed persistence. Release only after existing action markers or confirmed Earn/fuel balance state is persisted; normal risk veto/no-order cycles remain repeatable.
• Keep dry-run/disabled execution lock-free and reject unowned live mutation paths. No TTL, takeover, pin, dependency, workflow or runtime configuration changes.

Verification

• Existing expected-failure concurrency regression: actual RED (2 submissions), then GREEN (1 winner, 1 state read, 1 submission); expectedFailure removed.
• Hard-offline full suite with cleared environment and temporary HOME: 290 passed, 33 subtests passed.
• Ruff, diff check, uv pip check (67 packages), uv lock --check --offline passed.
• 5 production files and 7 existing test files only.

Runtime boundary

No broker/provider/cloud calls or deployments performed. Synthetic transactions do not establish Firestore permissions or real-account reconciliation. Stop old runners before adoption; no automatic owner deletion or takeover.