[jaygeorge]

Depends on #15710.

Description of the Problem

Combobox chips trim their text to x-height, which centres lowercase labels like field handles, but anything with capitals or digits ("UK", "2026", "United Kingdom") sits visibly high.

Validation rule chips and dictionary chips aren't trimmed at all, so they don't line up with combobox chips either.

What this PR Does

• Adds an st-text-trim-optical utility that trims to x-height and nudges the text down so it sits halfway between x-height and cap height.
• Combobox, validation rule and dictionary chips all use it.
• Combobox chips drop their own padding override and use the badge's minimum height from [6.x] Optically centre badge text #15710 instead.
• Replaces the st-text-trim-ex-alphabetic utility, which was only used by combobox chips.

Why halfway?

Chips hold whatever people type or pick, so a single field can easily mix lowercase handles, capitalised names and numbers. Trimming to x-height favours lowercase and trimming to cap height favours capitals, and either way half the chips look off.

Halfway keeps both close enough to centre that neither stands out. It's a slightly bigger nudge than badges get, as chips are larger and roomier.

Trimming per label would put chips on the same row on different baselines, which looks worse than either.

Before / After

How to Reproduce

1. Add a taggable field to a blueprint and enter a mix of tags like email, News, UK and 2026.
2. Compare the chips with 6.x in light and dark mode.
3. Do the same with a dictionary field (e.g. countries) and with the validation rules on any field in the blueprint editor.