Function read_flags_at 

pub fn read_flags_at(data: &[u8], offset: usize) -> Result<u8, ProgramError>

Read the flags byte from a data slice at offset, returning the value. Bounds-checked: AccountDataTooSmall if offset is out of range.

Pairs with SliceCursor::skip when you want to jump to a flags byte at a known position without reading all preceding fields.