fix: remove dead single-preset button semantics

[gooddev97]

Summary

• Render the single-preset indicator as a non-interactive, accessibility-hidden view instead of an enabled button with no action.
• Keep multi-preset controls interactive and unchanged.
• Document stable accessibility labels and formatValue guidance.

Verification

• bun run lint
• bun run typecheck
• bun run test (22 tests pass)
• bun run build
• bun run pack:check
• Manual VoiceOver/TalkBack check

Compatibility

• Platform(s): iOS and Android
• React Native version: 0.86.3 in the example app; public peer range >=0.81.0 <0.87
• Expo version or bare React Native: Expo SDK 57
• Dial Slider/Reanimated/Worklets/Gesture Handler/SVG/Linear Gradient versions: 0.1.0 / 4.5.1 / 0.10.1 / 2.32.x / 15.15.4 / 57.0.1

Contributor checklist

• No new component-renderer test was added; the repository currently has no accessibility-tree render harness.
• I updated public API documentation and examples where needed.
• I kept generated lib output out of the commit.
• I did not include secrets, credentials, or private user data.
• No breaking change or migration is required.

[ngocdevv]

Approved after successful automated verification.