Simulate a single transaction on top of a chain tip

Simulate a single transaction in an ephemeral block built on top of the given chain tip, or the canonical chain tip if the tip query parameter is omitted (no data is written in the MARF), and return its result, events, and execution cost. The simulation runs with the full tenure execution budget, independent of the cost already consumed in the current tenure. The transaction must be fully signed and valid (correct nonce, sufficient balance for the fee). The simulation enforces the same per-transaction wall-clock and memory limits the signers apply during block proposal validation (the connection_options.block_proposal_max_tx_execution_time_secs, block_proposal_max_tx_analysis_time_secs, and block_proposal_max_tx_mem_bytes options), so a transaction which exceeds them fails to simulate.

A tip naming a block that does not exist returns 404. A tip naming a block that exists but cannot be simulated by this endpoint (for example an epoch-2.x block) returns 400.