Retrieve a specific block trade by ID with full details.

Returns complete block trade information including status, trade details, signatures, and offers.

Access: Available to initiator, required signers, or accounts with submitted offers.

Returns:

• Block ID and status (CREATED, OFFER_COLLECTION, READY_TO_EXECUTE, EXECUTING, COMPLETED, CANCELLED)
• Market-specific trade details with orders and fill information
• All collected signatures from required signers
• Creation time, last update, expiration, and participant information

{
  "block_expiration": 1640995800000,
  "block_id": "block_456",
  "created_at": 1640995200000,
  "initiator": "0x123...abc",
  "last_updated_at": 1640995400000,
  "nonce": "67890",
  "parent_block_id": "block_123"
}