Ensures the dedicated "Bridge Plugin Demos" workspace exists in NBLOCKS_DASHBOARD, owned by the primary admin user, and returns its tenant id. Idempotent — subsequent calls return the same workspace. Plugin pre-setup scripts and standalone setup scripts use this to link SDK demo apps (SDK_APP, BRIDGE_NEXTJS_TEST_DASHBOARD, etc.) to a single dedicated workspace, separate from the developer's main admin workspace. The admin UI shows it as "Bridge Plugin Demos" under the primary admin user. Returns nulls on a fresh / unseeded DB — caller skips linking gracefully. GET /account/test/playwright/sdk-demos-workspace Headers: x-playwright-api-key: <your-api-key> Returns: { tenantId, name } where both may be null