fix(ui): improve Options legibility with Increase Transparency

[validatedev]

TL;DR

Keeps the footer Options control readable when Increase Transparency places it over light or similarly colored desktop backgrounds.

What was happening

• The custom Options capsule relied only on Liquid Glass over an already translucent footer.
• Light desktop colors could wash out the capsule boundary and make the control difficult to identify.

What this changes

• Adds an adaptive frosted material backing and separator beneath the Options Liquid Glass capsule in readable translucent modes.
• Preserves the existing opaque appearance and intentionally faint Drunk Mode.
• Documents the legibility behavior and adds regression coverage for the style selection.

Tests

• swift test --filter PopoverTransparencyStyleTests
• swift test (887 tests, 3 skipped, 0 failures)
• ./script/build_and_run.sh verify

Screenshots

Before:

After:

[validatedev]

@codex review

[chatgpt-codex-connector]

Codex Review: Didn't find any major issues. Delightful!

Reviewed commit: b2aa491292

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