feat(coding): add core host api composition

electron/api/routes/coding-route-errors.ts

@@ -0,0 +1,42 @@
+import type { ServerResponse } from 'node:http';
+import { CodingProjectServiceError } from '../../coding-projects/project-service';
+import { CodingConversationServiceError } from '../../coding-runtime/conversation-service';
+import { sendJson } from '../route-utils';
+
+export function sendCodingRouteError(res: ServerResponse, error: unknown): void {
+  if (error instanceof CodingProjectServiceError || error instanceof CodingConversationServiceError) {
+    sendJson(res, error.status, {
+      success: false,
+      code: error.code,
+      error: error.message,
+    });
+    return;
+  }
+  if (error instanceof SyntaxError) {
+    sendJson(res, 400, {
+      success: false,
+      code: 'CODING_REQUEST_INVALID',
+      error: 'Request JSON is invalid',
+    });
+    return;
+  }
+  sendJson(res, 500, {
+    success: false,
+    code: 'CODING_REQUEST_FAILED',
+    error: 'Coding request failed',
+  });
+}
+
+export function decodeRouteId(value: string): string {
+  try {
+    const decoded = decodeURIComponent(value).trim();
+    if (!decoded || decoded.length > 128 || decoded.includes('/')) throw new Error();
+    return decoded;
+  } catch {
+    throw new CodingConversationServiceError(
+      400,
+      'CODING_CONVERSATION_REQUEST_INVALID',
+      'Route identifier is invalid',
+    );
+  }
+}