Fix mouse clicks not firing combobox-commit when the input blurs

[cpruijsen]

Summary

The list listens on mousedown and on click. mousedown commits, and the click that follows it is skipped, so one mouse selection fires one combobox-commit and a blur handler that calls stop() no longer loses it (mousedown runs before blur; stop() removed the old click listener). A click with no preceding mousedown, such as option.click(), still commits, so the keyboard path is unchanged: commit() calls target.click() and the click listener fires the event with the click in detail.event. Non-primary buttons are ignored, matching click.

The guard holds the option the mousedown committed and is cleared by the next click anywhere in the document, so a press the pointer never completed cannot swallow a later click on that option.

For a mouse selection detail.event is now the mousedown event rather than the click. That follows from committing on mousedown.

Fixes #54.

Decision

The library listens on mousedown (the approach in #54) rather than leaving commit on click and adding an interactingWithList flag in the example, as github/auto-complete-element and github/text-expander-element do for this race. Closing the list on input blur is normal. Binding commit to click alone makes every such consumer lose the mouse path; the demo was the reproduction.

Test plan

• New test: mousedown -> blur/stop() -> click still fires one combobox-commit.
• New test: a direct option.click() fires one combobox-commit.
• New test: a mousedown whose click lands elsewhere does not suppress a later option.click().
• Fails with the old click-only listener; passes with mousedown plus the guarded click.
• Existing Enter and option-click tests still pass, including <a> options updating location.hash.
• npm test (eslint, tsc, Karma/Chrome Headless): 27 tests completed.

[llastflowers]

Thanks for working on this fix! Before we can merge this we need to:

• Preserve option.click() with a guarded click listener (as mentioned in PR description)
• Add a direct option.click() regression test
• Remove the new direct fireCommitEvent(target) call from the keyboard path: Let target.click() reach the click listener as it previously did, preserving the existing event order and detail.event value
• Ensure the guard resets when a mousedown is not followed by a click