fix: render cart toggle hidden title label as plain text

[kdaviduik]

Closes https://github.com/shop/issues/issues/84843.

Context

When options.toggle.contents.title is false (the default), the cart toggle renders a visually hidden label containing options.toggle.text.title. That label rendered the title as HTML instead of plain text. The visible title path already renders the same value as text.

Root Cause

ToggleView#readableLabel interpolated the title directly into an HTML string. That string is appended in wrapTemplate after Mustache has rendered the main template, so it never went through Mustache's escaping before being parsed via innerHTML.

Solution

Escape the title with Mustache.escape, the same escaper used for {{data.text.title}} in the visible title template. A regression test asserts that markup in the title is not parsed and that the label's text content matches the input exactly.

This does not change what screen readers announce. In manual testing, the announced name came from the toggle wrapper's aria-label, which is set via setAttribute and was already treated as plain text.

Risk Assessment

Low. The only behaviour change is that titles containing HTML or entities (e.g. &) are no longer parsed as markup in the hidden label, which matches the visible title and the aria-label.

[tgeselle]

I think we can remove that comment here