fix(free): keep focus after removing a selected chip (#288)

[MrDarkRoot]

Summary

• After a chip is removed, focus moves to the remaining chip's remove control. If it was the last chip, focus moves to the search field when that field is in the tab order, otherwise to Clear selected products.
• document.activeElement is not body. Focus uses preventScroll so the page does not jump. The no-JS submit path is unchanged.

Lab proof

Chrome 148 on http://127.0.0.1:18092, after copying this free-selection.js into the running acceptance lab:

• Two chips: Enter on the first remove control left focus on button.writeleash-chip__remove (Remove Harbor Tee…), not body. Scroll delta 0.
• Last chip: focus moved to #writeleash-free-product_search, not body.

Local bash .github/ci/pr-fast.sh: #133 PR_FAST PASS.

Do not merge. Only @MrDarkRoot merges.

Fixes #288