## Title
Add remote Git URL workspace import (clone to local path) like GitHub Desktop
## Summary
Add a new feature that allows users to import a workspace by providing a remote Git URL (`.git` URL), selecting a local destination folder, and having the app clone the repo locally before adding it as an active workspace.
## Problem
Current workspace onboarding only accepts local paths. Users must pre-clone repositories outside the app before adding them, unlike GitHub Desktop-style workflows.
## Requested Behavior
- Add a dedicated “Add Workspace from URL…” action (separate from existing local path add).
- Prompt for:
- Remote Git URL (required)
- Destination parent folder (required, directory picker)
- Optional target folder name (defaults to repo slug/name)
- App clones the repo to the selected path and then registers the resulting local repo as a workspace.
- New workspace should become the active workspace on success.
- Keep current local path add flow unchanged.
- Reject cloning if target path already exists and is non-empty.
- Use existing system git credential flow (SSH keys / credential helper), no new in-app token fields.
- Surface clear errors for invalid URL, missing destination, permission/network/auth failures, and destination conflicts.
## Acceptance Criteria
- [ ] New Tauri command exists: `add_workspace_from_git_url(url, destination_path, codex_bin?)` (or equivalent naming).
- [ ] Shared workspace core supports remote clone + persistence path.
- [ ] App command + daemon RPC surfaces updated for parity.
- [ ] New frontend service method added and used by workspace action.
- [ ] New UI prompt/modal for URL import.
- [ ] Existing local add action continues to work unchanged.
- [ ] Tests added/updated:
- [ ] frontend hook/action prompt validation and API invocation
- [ ] workspace add path + new remote add behavior
- [ ] backend/core validation for URL/path and destination conflict
- [ ] Manual check: importing `https://github.com/...git` with selected folder creates local repo and adds workspace.
## Tech Notes
- Reuse existing clone-related patterns where available (`run_git_command`, existing clone/core workspace patterns, modal/hook style).
- Menu integration: add new menu item for URL import and map to new modal/action.
- Keep API and event contracts in sync with frontend IPC expectations.
## Out of Scope
- No built-in credential manager UI in v1.
- No bulk remote import.
- No auto-rename collision fallback (reject and ask user).
## Suggested Labels
feature, workspace, tauri, frontend, backend
