pub const MARKET_DISCRIMINATOR_V1: [u8; 8];Expand description
8-byte discriminator for v1 market accounts: 7 fixed bytes (b"percmrk")
followed by a 1-byte layout version (0x01).
Note: percli v0.9 accounts use b"percmrkt" (last byte = 0x74 = 't'),
the legacy v0 marker. They must be migrated via migrate_header_v1 before
any other instruction can run against them.