ci(ops): squash commits on dev can fail commitlint and block the promotion PR #1130

Problem

The promotion PR #1128 failed commitlint because the head commit of dev (69e8b84, the squash of #1127) has a body line and a footer line over 100 characters (body-max-line-length, footer-max-line-length, plus a footer-leading-blank warning). The squash body is built from the PR's commits/description, so any PR with long lines can leave dev in a state where the next promotion fails this check. The commitlint check on the feature PR itself passed, because it lints that PR's head commit, not the squash commit that merge-when-green.mjs produces.

commitlint is not a required check on main, so the promotion was merged with --ignore commitlint (documented in #1128). That is a workaround, not a fix.

Task

Make the squash commit that lands on dev always pass the repo's commitlint config. For example, scripts/ops/merge-when-green.mjs sets an explicit squash commit_message that is lint-clean (wrapped at 100, footer separated by a blank line), or lints it before merging and fails early. Pick the smallest robust fix.

Acceptance

• A unit test in the existing scripts/ops test suite: a PR body with lines over 100 characters yields a squash message that passes commitlint.config.ts.
• promote.mjs no longer needs --ignore commitlint for this cause.
• Docs/Resources/RELEASE.md updated if the merge behavior changes.