test(sdk): enforce runtime bridge seam and explicit no-fallback behavior

sdk/src/query-runtime-seam-coverage.test.ts

@@ -0,0 +1,20 @@
+import { describe, it, expect, vi } from 'vitest';
+import { createGSDToolsRuntime } from './query-gsd-tools-runtime.js';
+
+describe('SDK Runtime Bridge seam coverage', () => {
+  it('exposes bridge as the single runtime seam', () => {
+    const runtime = createGSDToolsRuntime({
+      projectDir: '/tmp/project',
+      gsdToolsPath: '/tmp/gsd-tools.cjs',
+      timeoutMs: 1_000,
+      shouldUseNativeQuery: () => true,
+      execJsonFallback: vi.fn(async () => ({})),
+      execRawFallback: vi.fn(async () => ''),
+    });
+
+    expect(Object.keys(runtime)).toEqual(['bridge']);
+    expect(typeof runtime.bridge.resolve).toBe('function');
+    expect(typeof runtime.bridge.execute).toBe('function');
+    expect(typeof runtime.bridge.dispatchHotpath).toBe('function');
+  });
+});