fix: align git mount implementation with spec

- _checkout_branch now returns bool and falls back gracefully on failure
- Glob warning message includes matched file count
- Fix database model comment to reference remote_url
- Update tests for new branch checkout behavior

All 51 tests pass

apps/api/src/models/config_profile.py

@@ -41,7 +41,7 @@ class ConfigProfile(UUIDPrimaryKeyMixin, TimestampMixin, Base):
     )  # {"rel/path": "content", ...}
     git_mounts: Mapped[list] = mapped_column(
         JSON, default=list, nullable=False
-    )  # [{"repo_id": "uuid", "source_path": ".", "target_path": "/path", "branch": "main"}, ...]
+    )  # [{"remote_url": "https://github.com/user/repo.git", "source_path": ".", "target_path": "/path", "branch": "main"}, ...]
     is_default: Mapped[bool] = mapped_column(Boolean, default=False, nullable=False)
 
     user: Mapped["User"] = relationship()