fix(sign-push): force rebase so -S actually re-signs the tip

`git rebase <base>` is a no-op when HEAD is already a descendant of
<base>, which is the normal shape for a local branch built on top of
origin/main. Without `--force-rebase`, rebase short-circuits, `-S`
never runs, and the unsigned commit gets pushed and rejected by
required_signatures branch rules.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

pyproject.toml

@@ -4,7 +4,7 @@ build-backend = "setuptools.build_meta"
 
 [project]
 name = "git-maintainer-tools"
-version = "1.1.0"
+version = "1.1.1"
 description = "Small CLIs (git-setup-remotes, git-sign-push) for fork-based OSS maintainer workflows."
 readme = "README.md"
 requires-python = ">=3.10"