v0.12.0 — iOS 17 platform floor

Middle step of the coordinated stack-wide iOS 17 move (kadr v0.15 → kadr-ui v0.12 → reels-studio @Observable). Floor raised to iOS 17 / macOS 14 / tvOS 17 / visionOS 1. No behavior change — snapshot baselines unchanged.

Roadmap correction: v0.12 was pencilled in as the @Observable migration, but KadrUI holds no ObservableObjects (pure value-type SwiftUI). The @Observable migration lives in reels-studio; this floor bump unblocks it.

Changed

• Package.swift platforms → iOS 17 / macOS 14 / tvOS 17 / visionOS 1; Kadr floor → ≥ 0.15.0.
• 4 onChange(of:perform:) sites → iOS-17 two-parameter onChange.

Removed

• 40 redundant @available(iOS 16, …) annotations across all 14 source files.

Fixed

• Lingering .speed(curve:) test call → .speed(.curved(_:)) (Kadr removed the deprecated overloads in 0.14).

Compatibility

Requires Kadr ≥ 0.15.0. Consumers needing the iOS 16 floor stay on 0.11.x.

Full diff: v0.11.0...v0.12.0