feat: implement simple query service and enhance provider abstraction

- Introduced a new Simple Query Service to streamline basic AI queries, allowing for structured JSON outputs.
- Updated existing routes to utilize the new service, replacing direct SDK calls with a unified interface for querying.
- Enhanced provider handling in various routes, including generate-spec, generate-features-from-spec, and validate-issue, to support both Claude and Cursor models seamlessly.
- Added structured output support for improved response handling and error management across the application.

apps/server/src/providers/claude-provider.ts

@@ -99,6 +99,8 @@ export class ClaudeProvider extends BaseProvider {
       ...(maxThinkingTokens && { maxThinkingTokens }),
       // Subagents configuration for specialized task delegation
       ...(options.agents && { agents: options.agents }),
+      // Pass through outputFormat for structured JSON outputs
+      ...(options.outputFormat && { outputFormat: options.outputFormat }),
     };
 
     // Build prompt payload