TigerStyle: unchecked arithmetic in SDS::append()

[nerdsane]

Context

Found during code review of bitmap implementation (commit e9be18b).

Problem

src/redis/data/sds.rs:203 uses raw + in append():

let new_len = self.len() + other.len();

TigerStyle requires checked_add on all computed integers. While realistic Redis values cannot overflow usize on 64-bit (512MB limit), the convention requires explicit checked arithmetic.

Fix

let new_len = self.len().checked_add(other.len())
    .ok_or_else(|| /* return error or use expect with documented reason */)?;

Severity

Medium — pre-existing, not introduced by bitmap commits.

Found By

TigerStyle review agent (Issue 5)