test: add comprehensive test suite with 129 tests

- Add PTY interactive session tests
- Add SSE event streaming tests
- Add scheduled runs API tests
- Add edge case and error handling tests
- Add integration flow tests for user workflows
- Add respawn controller tests with edge cases
- Add session cleanup and resource management tests

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

vitest.config.ts

@@ -0,0 +1,16 @@
+import { defineConfig } from 'vitest/config';
+
+export default defineConfig({
+  test: {
+    globals: true,
+    environment: 'node',
+    include: ['test/**/*.test.ts'],
+    coverage: {
+      provider: 'v8',
+      reporter: ['text', 'json', 'html'],
+      include: ['src/**/*.ts'],
+      exclude: ['src/index.ts', 'src/cli.ts'],
+    },
+    testTimeout: 30000, // 30 seconds for integration tests
+  },
+});