bug(core): observe() ignores an annotated root element

[vamgan]

Summary

ctx.observe(rootElement) does not attach interaction listeners when rootElement itself has data-askable. Only annotated descendants are attached, so clicking/focusing the annotated root leaves context focus empty.

Root cause

packages/core/src/observer.ts resolves the root and calls:

rootEl.querySelectorAll<HTMLElement>('[data-askable]').forEach((el) => this.attach(el));

querySelectorAll() only returns descendants, not rootEl itself.

Verified reproduction

Against main at 40a3374:

1. Create a button with data-askable='{"id":"root"}'.
2. Call ctx.observe(button, { events: ['click'] }).
3. Click the button.
4. ctx.getFocus() remains null.

Observed output:

{"focus":null}

Proposed fix

When the root is an HTMLElement, attach it first if it has data-askable, then scan descendants. Preserve the existing Document behavior.

Also verify attribute mutation behavior when an observed root gains or loses data-askable after observation.

Acceptance criteria

• An annotated HTMLElement passed directly to observe() is interactive
• Annotated descendants continue to work
• An unannotated root does not produce focus
• Adding/removing data-askable on the observed root updates listener state
• unobserve() detaches the root listener
• Unit and browser E2E regression coverage is added