feat: implement MCP provider registry and service

- Add provider registry to manage LLM providers (Claude, Codex, Cursor, Gemini).
- Create provider routes for MCP server operations (list, upsert, delete, run).
- Implement MCP service for handling server operations and validations.
- Introduce abstract provider class and MCP provider base for shared functionality.
- Add tests for MCP server operations across different providers and scopes.
- Define shared interfaces and types for MCP functionality.
- Implement utility functions for handling JSON config files and API responses.

server/shared/interfaces.ts

@@ -0,0 +1,40 @@
+import type {
+  LLMProvider,
+  McpScope,
+  McpTransport,
+  ProviderMcpServer,
+  UpsertProviderMcpServerInput,
+} from '@/shared/types.js';
+
+
+/**
+ * MCP runtime contract for one provider.
+ */
+export interface IProviderMcpRuntime {
+  listServers(options?: { workspacePath?: string }): Promise<Record<McpScope, ProviderMcpServer[]>>;
+  listServersForScope(scope: McpScope, options?: { workspacePath?: string }): Promise<ProviderMcpServer[]>;
+  upsertServer(input: UpsertProviderMcpServerInput): Promise<ProviderMcpServer>;
+  removeServer(
+    input: { name: string; scope?: McpScope; workspacePath?: string },
+  ): Promise<{ removed: boolean; provider: LLMProvider; name: string; scope: McpScope }>;
+  runServer(
+    input: { name: string; scope?: McpScope; workspacePath?: string },
+  ): Promise<{
+    provider: LLMProvider;
+    name: string;
+    scope: McpScope;
+    transport: McpTransport;
+    reachable: boolean;
+    statusCode?: number;
+    error?: string;
+  }>;
+}
+
+
+/**
+ * Provider contract that both SDK and CLI families implement.
+ */
+export interface IProvider {
+  readonly id: LLMProvider;
+  readonly mcp: IProviderMcpRuntime;
+}