Resolves all validator errors flagged by the new
tools/validate-sidebar-order.js check.
English (docs/{explanation,how-to,reference}/):
- Renumbered to remove duplicates; established reading order
for new explanation pages added since orders were last set.
Translations (cs, fr, vi-vn, zh-cn):
- Mirrored English structural ordering where files exist, then
compacted to 1..N within each directory to eliminate gaps
caused by missing translation files.
Non-blocking drift warnings remain where translation directories
have fewer files than English; these are expected per the
validator's design.
ac7647d171