fix: use working clones for git repos

- Create normal working clones for remote repositories
- Initialize blank repositories with a main branch
- Align pull and branch helpers with unborn HEAD handling
- Gate fetch/pull on repositories with a remote

Quality gates: vitest repositories-settings-tab (passed); api pytest blocked by missing fastapi in environment

openspec/changes/git-repo-working-clones/tasks.md

@@ -0,0 +1,19 @@
+## 1. Backend - Repository Creation
+
+- [x] 1.1 Switch clone-based repository creation from mirror clones to normal working clones
+- [x] 1.2 Initialize blank repositories with a default branch name
+- [x] 1.3 Preserve remote preflight and clear error handling
+
+## 2. Backend - Git Sync Helpers
+
+- [x] 2.1 Update pull behavior to use the current tracked branch when available
+- [x] 2.2 Make branch helpers tolerate unborn HEAD in blank repos
+
+## 3. Tests
+
+- [x] 3.1 Add unit coverage for clone creation and blank repo initialization
+- [x] 3.2 Add coverage for pull behavior on working clones and blank repos
+
+## 4. Quality Gates
+
+- [ ] 4.1 Run targeted API tests