v0.28.4

Move comment out from between OpenMP pragma and for-loop

MSVC's OpenMP 2.0 pragma parser requires the for-statement to be the
statement immediately following the pragma, with no intervening tokens
(including comment blocks). The previous commit kept the explanatory
comment between the pragma and the for, which MSVC silently dropped
the pragma-to-loop association for and re-emitted C3015.

Also pre-compute the int upper bound `l_size_i` so the test expression
is a plain `int < int` with no cast — MSVC's canonical-form check
prefers this.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>