v5.3.0 — seller lockCadence control + buyer covered-settle tolerance

• tabOrExactMiddleware now forwards lockCadence (thresholdAtomic / onClose) to the tab rail — dual-rail sellers gain full crystallization cadence control, including disarm (onClose: false). Omitted config keeps prior defaults exactly.
• Loud crystallize logging: every lock attempt outcome logs through one choke point; silent .catch(() => {}) seller-protection failures are gone.
• Chain-frontier baseline seeding: fresh seller ledger entries seed from max(spent, crystallizedCumulative), closing the resume over-delivery window; fails closed on stale vouchers.
• Buyer Tab.close() tolerates settles fully covered by seller-side locks (200 covered_by_frontier verified against the body's own amounts, BigInt-strict, fail-closed; deploy-skew 409 tolerance) — the revoke now proceeds on covered settles instead of stranding the session.

Note: 5.2.0's tarball included a stray public pricing doc (assets/openai-pricing.md) which also rode 5.3.0 — harmless public content, excluded from all future releases via the files allowlist fix in this commit.