v1: component smoke test for App.tsx

[gorlix]

Context

Only the pure logic (computeLassoRect, pickInitialLanguage) is unit-tested. App.tsx (mount, tap handler, busy-guard reset, SDK orchestration) has no test. The sn-plugin-lib jest mock already exists (__mocks__/sn-plugin-lib.js).

Goal

A component/smoke test for App.tsx that mounts it with the mocked SDK and asserts the tap flow.

Approach

• Render App with react-test-renderer (already a devDep) using the existing mock.
• Simulate a press on the overlay; assert the mocked lassoElements → setLassoBoxState → closePluginView sequence is called with the expected rect.
• Assert the busy-guard is reset (a second simulated tap also fires the flow), guarding the regression fixed in fix(ui): reset busy guard so reopening the plugin works #14.

Acceptance criteria

• Test mounts App without a device and passes in CI.
• Asserts the lasso/close call order and the busy-reset behavior.

References

• __mocks__/sn-plugin-lib.js, jest.config.js
• Regression context: PR fix(ui): reset busy guard so reopening the plugin works #14 (busy-guard reset)