CHANGELOG and check_mutation_thm_trail.py describe the ThM-decision requirement as pre-existing; #306 introduced it #318

CHANGELOG.md and the header comment of scripts/check_mutation_thm_trail.py (added in #306) say the record-sourcing process "already requires" stating the ThM decision in the commit message. It did not. The phrase "ThM decision" first appears in the #306 change itself, and no earlier file states the requirement (checked with git log -S and a repo-wide grep).

The expectation is reasonable as a new rule, and CONTRIBUTING.md states it as one. The two descriptive passages should say the same: this change introduces it.

Scope: wording in CHANGELOG.md and the script header comment only. No behavior change; the check's output is identical before and after (compared byte for byte).