feat(mirror,create): make MIRRORS single source of truth and exclude PyPI from git config

- Treat MIRRORS as the only authority for mirror URLs
- Filter non-git URLs (e.g. PyPI) from git remotes and push URLs
- Prefer SSH git URLs when determining primary origin
- Ensure mirror probing only targets valid git remotes
- Refactor repository create into service-based architecture
- Write PyPI metadata exclusively to MIRRORS, never to git config
- Add integration test verifying PyPI is not written into .git/config
- Update preview and unit tests to match new create flow

https://chatgpt.com/share/69415c61-1c5c-800f-86dd-0405edec25db

src/pkgmgr/actions/repository/create/mirrors.py

@@ -0,0 +1,54 @@
+from __future__ import annotations
+
+from typing import Any, Dict
+
+from pkgmgr.actions.mirror.io import write_mirrors_file
+from pkgmgr.actions.mirror.setup_cmd import setup_mirrors
+
+Repository = Dict[str, Any]
+
+
+class MirrorBootstrapper:
+    """
+    MIRRORS is the single source of truth.
+
+    We write defaults to MIRRORS and then call mirror setup which will
+    configure git remotes based on MIRRORS content (but only for git URLs).
+    """
+
+    def write_defaults(
+        self,
+        *,
+        repo_dir: str,
+        primary: str,
+        name: str,
+        preview: bool,
+    ) -> None:
+        mirrors = {
+            # preferred SSH url is supplied by CreateRepoPlanner.primary_remote
+            "origin": primary,
+            # metadata only: must NEVER be configured as a git remote
+            "pypi": f"https://pypi.org/project/{name}/",
+        }
+        write_mirrors_file(repo_dir, mirrors, preview=preview)
+
+    def setup(
+        self,
+        *,
+        repo: Repository,
+        repositories_base_dir: str,
+        all_repos: list[Repository],
+        preview: bool,
+        remote: bool,
+    ) -> None:
+        # IMPORTANT: do NOT set repo["mirrors"] here.
+        # MIRRORS file is the single source of truth.
+        setup_mirrors(
+            selected_repos=[repo],
+            repositories_base_dir=repositories_base_dir,
+            all_repos=all_repos,
+            preview=preview,
+            local=True,
+            remote=True,
+            ensure_remote=remote,
+        )