## Context

The current repository creation flow already supports cloning remote repositories via `remote_url` and can normalize pasted browser URLs. However, the UI asks for a full URL, which is awkward for the fixed provider `git.commumedia.org`. The requested behavior is to enter `owner` and `repo`, check whether the repository exists, and clone only if it does.

## Goals / Non-Goals

**Goals:**
- Accept SSH-only `owner` and `repo` inputs for cloning from `git.commumedia.org`
- Verify repository existence before clone
- Preserve full URL paste as a fallback path
- Preserve blank repository creation
- Reuse the existing repository create endpoint and shared dialog

**Non-Goals:**
- Supporting multiple git providers
- Adding a remote repository discovery API
- Supporting HTTPS clone flow for the new structured path
- Changing repository storage or clone behavior beyond preflight validation

## Decisions

**1. Provider assumption**
- Hardcode `git.commumedia.org` for the structured clone path
- Build SSH URLs as `git@git.commumedia.org:{owner}/{repo}.git`

**2. Existence check**
- Use `git ls-remote` on the constructed SSH URL before cloning
- If the command fails, surface a repository-not-found/inaccessible error and do not clone

**3. UI structure**
- Keep the shared repository creation dialog as the single entry point
- In clone mode, collect `owner` and `repo` instead of asking for a full URL
- Keep an advanced paste-URL fallback for existing behavior and browser URL parsing
- Keep blank repository creation available in the same dialog

**4. Backend behavior**
- Reuse `POST /projects/{project_id}/repositories`
- Add preflight logic before the existing `git clone --mirror`
- Leave the database schema unchanged

## Risks / Trade-offs

**[Risk] SSH auth may still fail even if the repo exists** → Mitigation: preflight error should be explicit and user-facing.
**[Risk] Command availability** → Mitigation: reuse the same `git` dependency already required for cloning.
**[Risk] UI complexity** → Mitigation: keep the dialog shared and minimal, with fallback URL paste.