feat: implement repository clone mode with SSH key support

- Add clone_mode and branch fields to tool_instances
- Add ssh_key_id to git_repositories for per-repo SSH key assignment
- Implement host-side git cloning with branch selection (default: main)
- Mount SSH keys into containers for git operations in clone mode
- Add dirty state check on clone-mode instance deletion with confirmation
- Update SessionsPage with mount/clone selector, branch input, SSH key display
- Add SSH key selector to repository creation form
- Add dirty delete confirmation modal with changed files list
- Update API schemas and endpoints for new fields
- Sync delta specs to main specs (git-repo, tool-instances, repo-clone-mode)
- Archive completed OpenSpec change: repo-clone-mode-with-ssh
- Document git requirement for custom tool types

Quality gates: Frontend typecheck and build passed
OpenSpec: repo-clone-mode-with-ssh archived with all tasks complete

openspec/changes/sessions-hub/design.md

@@ -1,120 +0,0 @@
-# Sessions Hub - Design
-
-## Architecture
-
-```
-Sessions Hub
-├── Navigation
-│   └── "Sessions" tab (between Dashboard and Projects)
-│       └── Badge with active session count
-├── SessionsPage
-│   ├── Last Session Section
-│   │   └── Quick access card with resume button
-│   ├── Active Sessions Section
-│   │   └── Grid of active session cards
-│   ├── Recent Sessions Section
-│   │   └── List of recent sessions
-│   └── Create Session Section
-│       └── Project selector + tool type selector
-└── User Config
-    └── last_session_id field
-```
-
-## Component Design
-
-### SessionsPage
-
-**Sections:**
-1. **Last Session** (if exists)
-   - Large card showing last session details
-   - "Resume" button to open the workspace
-   - Shows project, repository, tool type
-
-2. **Active Sessions**
-   - Grid of cards for running instances
-   - Each card: name, type, status badge, action buttons
-   - Actions: Open, Stop, Restart, Delete
-
-3. **Recent Sessions**
-   - List of last 5 sessions (any status)
-   - Compact list view with status indicators
-   - Click to navigate to workspace
-
-4. **Create New Session**
-   - Project dropdown (all user's projects)
-   - Repository dropdown (filtered by project)
-   - Tool type dropdown
-   - Display name input
-   - "Create" button
-
-### AppShell Updates
-
-**Navigation:**
-```
-Dashboard | Sessions (3) | Projects | SSH Keys | Tool Types | Settings
-```
-
-**Badge:**
-- Shows count of active (running) sessions
-- Updates via existing sessions polling
-
-### User Config Extension
-
-**New field:**
-```typescript
-interface UserConfig {
-  // existing fields...
-  last_session_id: string | null;
-}
-```
-
-**Update timing:**
-- Set when creating a new session
-- Set when opening/resuming a session
-
-## Data Flow
-
-### Loading Sessions Page
-1. Fetch user config (for last_session_id)
-2. Fetch all user sessions via `/users/me/sessions`
-3. Filter into active vs recent
-4. Display last session if available
-
-### Creating Session
-1. User selects project, repo, tool type
-2. POST to `/projects/{id}/repositories/{id}/instances`
-3. On success: update user config with last_session_id
-4. Refresh sessions list
-
-### Resuming Session
-1. User clicks "Resume" on last session
-2. Navigate to workspace with session active
-3. Update user config (reinforce as last)
-
-## API Changes
-
-### GET /users/me/sessions
-Already exists - returns all sessions for user.
-
-### PATCH /users/me/config
-Already exists - add `last_session_id` to config schema.
-
-## Technical Details
-
-**Frontend:**
-- New page: `pages/sessions.tsx`
-- Update: `app-shell.tsx` for navigation
-- Update: `api/settings.ts` for config type
-- Update: `state/sessions.tsx` for badge count
-
-**Backend:**
-- Update: `models/user_config.py` schema
-- Update: `api/user_config.py` to accept last_session_id
-
-**No new backend endpoints needed** - reuse existing APIs.
-
-## Error Handling
-
-- No sessions: Show empty state with "Create your first session" CTA
-- Failed to load: Show error with retry button
-- Create failed: Show error message, keep form open