Extract MCP server settings out of the settings controller and agents tab into a
dedicated frontend MCP module. The settings UI now delegates MCP rendering and
behavior to a single module that only needs the selected provider and current
projects.
Changes:
- Add `src/components/mcp` as the single frontend MCP module
- Move MCP server list rendering into `McpServers`
- Move MCP add/edit modal into `McpServerFormModal`
- Move MCP API/state logic into `useMcpServers`
- Move MCP form state/validation logic into `useMcpServerForm`
- Add provider-specific MCP constants, types, and formatting helpers
- Use the unified `/api/providers/:provider/mcp/servers` API for all providers
- Support MCP management for Claude, Cursor, Codex, and Gemini
- Remove old settings-owned Claude/Codex MCP modal components
- Remove old provider-specific `McpServersContent` branching from settings
- Strip MCP server state, fetch, save, delete, and modal ownership from
`useSettingsController`
- Simplify agents settings props so MCP only receives `selectedProvider` and
`currentProjects`
- Keep Claude working-directory unsupported while preserving cwd support for
Cursor, Codex, and Gemini
- Add progressive MCP loading:
- render user/global scope first
- load project/local scopes in the background
- append project results as they resolve
- cache MCP lists briefly to avoid slow tab-switch refetches
- ignore stale async responses after provider switches
Verification:
- `npx eslint src/components/mcp`
- `npm run typecheck`
- `npm run build:client`
