Instant Finality Query Support

Labels: ux, latency, finality

Summary:
Introduce immediate transaction finality feedback. Once a transaction reaches intra-block finality via the scheduler’s MainSche_Finality step, it becomes instantly queryable.

Subtasks:

• Expose finalized transactions through API immediately after intra-block finalization.
• Implement fast lookup indexing during execution.
• Benchmark end-to-end finality latency improvements.

Rationale:
Reduces single-transaction latency from ~500ms to sub-100ms. This is critical for real-time applications such as trading, gaming, and high-frequency microservices.