[redonkulus]

Fixes #568, fixes #569.

Problem

The i13n click listener is a native listener on the element, so it runs before React's onClick handlers (delegated to the root). For links and submit buttons it called e.preventDefault() itself, then navigated or submitted in code (location.assign / form.submit()) after the beacon. A later preventDefault() from user code had no effect.

Since #391 (switch to currentTarget), this means:

• [3.x] e.preventDefault() from the inner I13nButton can not stop the parent's <form> submit #569: an I13nButton inside a <form> submits even when its onClick calls preventDefault(). 2.x never touched buttons (no href), so the browser handled submit natively.
• [3.x] e.preventDefault() from the inner button can not stop the parent's <I13nAnchor> href redirection #568: an I13nAnchor navigates even when an inner button's onClick calls preventDefault(). 2.x avoided this by accident: e.target was the inner button, so it took the form-submit path with no form.

Fix (src/libs/clickHandler.js)

• Record whether any handler cancelled the click, before (e.defaultPrevented) or after the i13n listener (by wrapping e.preventDefault on the event). Skip the redirect/submit if so. The click beacon still fires.
• Defer the redirect with setTimeout(…, 0). With no plugin handling the event, the beacon callback runs synchronously, before React's handlers.
• Submit with form.requestSubmit(submitter) when available, so onSubmit handlers and constraint validation run. form.submit() skips both. Falls back to form.submit().

Behavior change to note

Redirects and submits now happen one macrotask later than before. In practice this is invisible, since they already waited for the beacon when plugins were registered.

Tests

• src/libs/tests/clickHandler.test.js: unit tests for prevented-before, prevented-after (link and form), and requestSubmit. The two _top/_parent tests now wait for the deferred redirect.
• src/components/tests/preventDefault.test.jsx: end-to-end tests that reproduce both issue scenarios with real I13nButton / I13nAnchor and React handlers, plus the unprevented happy paths.

All 6 new tests fail on master and pass with this change. Full suite: 60 passed, 1 skipped. npm run lint is clean.

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