fix: address code review comments - remove unused imports, fix 304 response, add fail-fast for string handlers

Co-authored-by: hotlong <50353452+hotlong@users.noreply.github.com>

Author: Copilot

examples/rest-server-example.ts

@@ -5,7 +5,7 @@
  * generate RESTful CRUD endpoints for your ObjectStack application.
  */
 
-import { RestServer, HttpServer } from '@objectstack/runtime';
+import { RestServer } from '@objectstack/runtime';
 import type { IProtocolProvider } from '@objectstack/runtime';
 
 /**

packages/runtime/src/http-server.ts

@@ -1,4 +1,4 @@
-import { IHttpServer, IHttpRequest, IHttpResponse, RouteHandler, Middleware } from '@objectstack/core';
+import { IHttpServer, RouteHandler, Middleware } from '@objectstack/core';
 
 /**
  * HttpServer - Unified HTTP Server Abstraction

packages/runtime/src/rest-server.ts

@@ -1,7 +1,6 @@
-import { IHttpServer, RouteHandler } from '@objectstack/core';
+import { IHttpServer } from '@objectstack/core';
 import { RouteManager } from './route-manager';
-import { RestServerConfig, CrudOperation } from '@objectstack/spec/api';
-import { ObjectStackProtocol } from '@objectstack/spec/api';
+import { RestServerConfig } from '@objectstack/spec/api';
 
 /**
  * RestServer
@@ -221,7 +220,7 @@ export class RestServer {
                             });
 
                             if (result.notModified) {
-                                res.status(304).json({});
+                                res.status(304).send();
                                 return;
                             }
 

packages/runtime/src/route-manager.ts

@@ -61,9 +61,16 @@ export class RouteManager {
      * @param entry - Route entry with method, path, handler, and metadata
      */
     register(entry: Omit<RouteEntry, 'handler'> & { handler: RouteHandler | string }): void {
-        const handler = typeof entry.handler === 'string' 
-            ? this.resolveHandler(entry.handler)
-            : entry.handler;
+        // Validate handler type - string handlers not yet supported
+        if (typeof entry.handler === 'string') {
+            throw new Error(
+                `String-based route handlers are not supported yet. ` +
+                `Received handler identifier "${entry.handler}". ` +
+                `Please provide a RouteHandler function instead.`
+            );
+        }
+        
+        const handler: RouteHandler = entry.handler;
 
         const routeEntry: RouteEntry = {
             method: entry.method,
@@ -200,13 +207,6 @@ export class RouteManager {
                 throw new Error(`Unsupported HTTP method: ${method}`);
         }
     }
-    
-    /**
-     * Resolve handler by name (placeholder for future handler registry)
-     */
-    private resolveHandler(handlerName: string): RouteHandler {
-        throw new Error(`Handler resolution not implemented: ${handlerName}`);
-    }
 }
 
 /**