PR #272 had green CI and GitHub reported `mergeable: true`, but `rebaseable: false` prevented merging in this rebase-only repository. The babysitter could incorrectly call this ready.

Check the effective merge method from repository settings and branch rules. For rebase-only branches, false replayability schedules a rebase and unknown replayability defers verification. Refresh inventory advice before dispatch, preserving parent ordering, opt-outs and exact head/base checks. Squash and merge repositories retain their existing behavior.

Validation: both original regressions failed before the fix; all 162 maintenance tests (1,067 assertions), formatting and repository CI checks pass. Independent review caught and verified a fresh-confirmation edge case.