release: v3.10.0 (a second session can no longer erase your plan in silence)

Version bump across the 19 parity-locked files, CHANGELOG, CONTRIBUTORS
and the README releases table.

Closes #217. Acts on the #130 drift audit without deleting the language
variants: they carry 39.8K of the project's 89.3K installs, and skills.sh
has no pruning job, so removing the directories would have left five
permanent listings advertising an install that fails rather than taking
them down. #130 stays open for the one cost that remains, the five extra
descriptions per session on the plugin route.

Suite 411 to 417.