fix: validate aimock fixtures at load time to prevent runtime 500s

Follow-up to CopilotKit#3971. aimock supports fixture schema validation at startup via
--validate-on-load, but it's opt-in. The showcase Dockerfile did not pass
the flag, so fixtures with unrecognized response keys (e.g. "text" instead
of "content") loaded silently and only failed at request time with HTTP 500.
That's what crashed crewai-crews on startup.

Changes:
- showcase/aimock/Dockerfile: pass --validate-on-load so broken fixtures
  fail the container boot, not individual requests.
- showcase/scripts/__tests__/aimock-fixtures.test.ts: new vitest spec that
  loads feature-parity.json and smoke.json via @copilotkit/aimock's
  loadFixtureFile + validateFixtures and asserts zero errors. Runs as part
  of the existing showcase-validate CI workflow.
- showcase/scripts/package.json: add @copilotkit/aimock dependency for the
  validator import.

Verified red-green: with the pre-CopilotKit#3971 broken "text" fixtures, validateFixtures
flags 5 errors; post-CopilotKit#3971 it returns zero. Docker red-green: container with
an intentionally broken fixture fails to start with "Validation failed: 1
error(s)" and non-zero exit.

Author: jpr5

pnpm-lock.yaml

@@ -6,5 +6,6 @@ CMD ["--proxy-only", \
      "--provider-anthropic", "https://api.anthropic.com", \
      "--provider-gemini", "https://generativelanguage.googleapis.com", \
      "--fixtures", "/fixtures", \
+     "--validate-on-load", \
      "--host", "0.0.0.0", \
      "--port", "4010"]

showcase/aimock/Dockerfile

@@ -0,0 +1,37 @@
+import { describe, it, expect } from "vitest";
+import path from "path";
+import { loadFixtureFile, validateFixtures } from "@copilotkit/aimock";
+
+const AIMOCK_DIR = path.resolve(__dirname, "..", "..", "aimock");
+
+const FIXTURE_FILES = ["feature-parity.json", "smoke.json"];
+
+describe("showcase aimock fixtures", () => {
+  for (const file of FIXTURE_FILES) {
+    it(`${file} loads and validates with zero errors`, () => {
+      const filePath = path.join(AIMOCK_DIR, file);
+      const fixtures = loadFixtureFile(filePath);
+
+      // If loadFixtureFile returns [], the file itself is broken (unreadable,
+      // invalid JSON, or missing "fixtures" array). Treat as fatal.
+      expect(
+        fixtures.length,
+        `${file} produced 0 fixtures — file is unreadable or malformed`,
+      ).toBeGreaterThan(0);
+
+      const results = validateFixtures(fixtures);
+      const errors = results.filter((r) => r.severity === "error");
+
+      if (errors.length > 0) {
+        const detail = errors
+          .map((e) => `  [${e.fixtureIndex}] ${e.message}`)
+          .join("\n");
+        throw new Error(
+          `${file} has ${errors.length} fixture validation error(s):\n${detail}`,
+        );
+      }
+
+      expect(errors).toEqual([]);
+    });
+  }
+});

showcase/scripts/__tests__/aimock-fixtures.test.ts

@@ -14,6 +14,7 @@
     "test:watch": "vitest"
   },
   "dependencies": {
+    "@copilotkit/aimock": "^1.10.0",
     "@playwright/test": "^1.59.1",
     "ajv": "^8.17.1",
     "ajv-formats": "^3.0.1",