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/ui-redesign-home-settings/tasks.md

@@ -1,34 +0,0 @@
-# UI Redesign - Tasks
-
-## 1. Visual System
-
-- [ ] Update global typography to Inter
-- [ ] Refine color tokens for the new warm editorial palette
-- [ ] Add styling for new home sections and settings tabs
-
-## 2. Navigation and Routing
-
-- [ ] Remove Sessions from top-level navigation
-- [ ] Keep SSH Keys, Tool Types, and Tool Configs accessible from Settings tabs
-- [ ] Add redirects for legacy top-level config routes
-- [ ] Redirect `/sessions` to `/`
-
-## 3. Home Page
-
-- [ ] Redesign the home page as an overview of open sessions and projects
-- [ ] Add summary cards and hero actions
-- [ ] Reuse existing session and project data
-- [ ] Keep create/open session actions available
-
-## 4. Settings Hub
-
-- [ ] Turn Settings into a tabbed hub
-- [ ] Build General, SSH Keys, Tool Types, and Tool Configs tabs
-- [ ] Reuse existing APIs and forms
-- [ ] Keep the Project settings page separate
-
-## 5. Cleanup and Verification
-
-- [ ] Remove obsolete top-level pages from navigation flow
-- [ ] Update tests for the new landing page and redirects
-- [ ] Run typecheck, lint, and build