theme: evaluate a uniform focus-style model in air tokens (upstream nuxt/ui#6576)

[IgorShevchik]

Context

Upstream nuxt/ui shipped b026ca2c — feat(theme): uniformize focus styles across components (nuxt/ui#6576) — a large change (~50 theme files, 200+ files incl. snapshots) that replaces nuxt/ui's per-component focus styling with a single uniform pattern:

outline-{color}/25 focus-visible:outline-3   /* + focus-visible:ring-{color} where a ring is also kept */

built on nuxt/ui's options.theme.colors loops and semantic tokens (outline-inverted, ring-accented, bg-{color}, …), plus:

• a base reset a:focus-visible { outline-offset: 0 } in src/runtime/index.css;
• overflow: hidden added to the accordion/collapsible keyframes in src/runtime/keyframes.css.

Decision in the sync stream — SKIPPED (no-op)

This commit is not portable 1:1 to b24ui and was recorded as a skip in the sync ledger (cursor advanced, no source change). Rationale:

• b24ui has its own focus-styling system based on air-design tokens — e.g. focus-visible:ring-1 focus-visible:ring-inset focus-visible:ring-(--b24ui-border-color), --ui-color-design-selection-content, style-blurred-bg-input — which is intentionally different from nuxt/ui's generic outline/ring model.
• b24ui has no options.theme.colors (no per-color compound loops), so the upstream structure (outline-${color}/25, bg-${color}, …) has no equivalent.
• Adopting the upstream model would overwrite b24ui's air design system focus styles — a design regression, not a faithful port.

Scope of this issue (evaluate, don't blindly port)

Decide deliberately whether b24ui wants a uniform focus model expressed in air tokens, and if so design + apply it:

• Define a single air-token focus pattern (the b24ui analogue of outline-3 + translucent ring) and apply it consistently across components, replacing the current per-component focus classes.
• Consider the two generic, design-agnostic bits from upstream that would apply cleanly if desired:
  • a:focus-visible { outline-offset: 0 } base reset (Chromium link focus) in src/runtime/index.css;
  • overflow: hidden in the accordion/collapsible @keyframes in src/runtime/keyframes.css (animation-clipping correctness, unrelated to focus).
• Regenerate component snapshots after any focus-style change.

References

• Upstream commit: b026ca2cdb0e4d6aff6d271a95e2d7e5e1bd7e3f (feat(theme): uniformize focus styles across components nuxt/ui#6576)
• Sync ledger: .sync/nuxt-ui.json → b026ca2c… entry (decision: skip)
• Related: b24ui focus tokens live in src/runtime/air-design-tokens/ and per-component src/theme/*.ts

No behaviour change has been made by the sync stream; this is a design decision to be made separately.