Fix mikado-branch-invariant-check not validating incoming commits

The commit-msg hook had `pass_filenames: false`, which prevented
pre-commit from passing the commit message file path. Without it,
the hook only validated existing branch history and never checked
the incoming commit against ordering rules — plan-after-impl was
silently accepted.

Remove `pass_filenames: false` so the pending commit is included
in invariant validation.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

.pre-commit-config.yaml

@@ -117,7 +117,6 @@ repos:
         entry: mise run mikado-branch-invariant-check
         language: system
         always_run: true
-        pass_filenames: false
         stages: [commit-msg]
 
   # Documentation validation