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/specs/opencode-web-server/spec.md

@@ -0,0 +1,39 @@
+## ADDED Requirements
+
+### Requirement: OpenCode runs a web server
+
+The system SHALL configure OpenCode containers to run a web server accessible on port 3000.
+
+#### Scenario: OpenCode container starts
+- **GIVEN** an OpenCode tool instance
+- **WHEN** the container starts
+- **THEN** a web server is running on port 3000 inside the container
+- **AND** the server serves a web terminal interface
+
+### Requirement: OpenCode exposes web interface
+
+The system SHALL mark OpenCode as having both terminal and web interfaces.
+
+#### Scenario: OpenCode instance created
+- **GIVEN** a new OpenCode instance
+- **WHEN** the instance list is displayed
+- **THEN** both "Open" and "Terminal" buttons are shown
+
+### Requirement: OpenCode web terminal uses correct port
+
+The system SHALL use port 3000 when creating tunnels for OpenCode instances.
+
+#### Scenario: Tunnel created for OpenCode
+- **GIVEN** an OpenCode instance with `default_port: 3000`
+- **WHEN** the instance starts and creates a tunnel
+- **THEN** the tunnel targets `http://container-name:3000`
+
+### Requirement: OpenCode web terminal displays properly
+
+The system SHALL serve a functional web terminal interface for OpenCode.
+
+#### Scenario: User opens OpenCode web UI
+- **GIVEN** a running OpenCode instance
+- **WHEN** the user clicks the "Open" button
+- **THEN** a new tab opens with the OpenCode web interface
+- **AND** the interface shows a terminal connected to the OpenCode process