test(#226,#227,#228): Add E2E integration tests for agent orchestration

Add comprehensive E2E test suites covering:
- Full agent lifecycle (spawn → running → completed/failed) - 7 tests
- Killswitch emergency stop mechanism (single/all/partial) - 5 tests
- Concurrent agent spawning and isolation - 5 tests

Includes vitest config for integration test runner with 30s timeout.

Fixes #226
Fixes #227
Fixes #228

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

apps/orchestrator/tests/integration/vitest.config.ts

@@ -0,0 +1,10 @@
+import { defineConfig } from "vitest/config";
+
+export default defineConfig({
+  test: {
+    globals: true,
+    environment: "node",
+    include: ["**/*.e2e-spec.ts"],
+    testTimeout: 30000,
+  },
+});