Shiki's github-light-default colors comments #6e7781 (~4.2:1 on the code
card background), which is borderline unreadable at the 11px code font
size — and worst for shell snippets, where a single `#` turns the rest
of the line into one long comment span. Remap light-mode comments to
GitHub's darker muted gray (#57606a, ~6.4:1) via per-theme
colorReplacements. Dark mode (~6.1:1) reads fine and is left untouched.
0bc616ecf9