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/proposal.md

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+## Why
+
+The current repository creation flow creates mirrored bare repositories for clone-based repos. That breaks the workspace model because the UI and file editing features expect a normal working clone with an initial branch, remote tracking, and pull/fetch behavior that works from a checked-out branch.
+
+## What Changes
+
+- Create clone-based repositories as normal working clones instead of mirrors
+- Initialize blank repositories as working clones with an initial branch when needed
+- Ensure newly created repos have a usable current branch for workspace browsing and commits
+- Update pull semantics to use the current tracked branch when available
+- Keep fetch behavior available for remote-synced repositories
+
+## Impact
+
+- Backend: repository creation and git control helpers
+- Backend tests: clone, pull, and empty-repo branch behavior
+- Frontend: no intentional UX change beyond sync behavior becoming reliable