feat(adaptive-window): add salt-adaptive-window module

[Moriafly]

Introduce a new KMP module salt-adaptive-window under package com.moriafly.salt.adaptive.window that lets code determine the device screen form factor and the available window size class at runtime.

Public API:

• DeviceFormFactor (Phone, Tablet, Foldable, Desktop, Car, Unknown)
• WindowSizeClass (Compact, Medium, Expanded) at the Material 3 breakpoints <600dp / 600-840dp / >=840dp
• SaltAdaptiveWindow(formFactor, sizeClass)
• LocalSaltAdaptiveWindow for ambient access from deeply nested code
• currentSaltAdaptiveWindow() as the platform expect/actual source

Why a separate module rather than reusing material3-adaptive: Google's androidx.compose.material3.adaptive is Android-only and deliberately has no device-type concept, but this library also targets desktop JVM and iOS, where "desktop" is a real distinct form factor. DeviceFormFactor is therefore documented as an interaction signal only (touch vs pointer), and layout breakpoints must be driven by sizeClass, because a tablet in split-screen can still have a Compact window.

LocalSaltAdaptiveWindow defaults to error(...) instead of a silent fallback, matching LocalSaltWindowInfo in ui2: reading it without a provider is a wiring mistake and should fail loudly rather than report a wrong form factor. The provider wiring is intentionally not part of this change.

Naming follows the current Google convention of a current prefix for a @composable that recomputes on every recomposition rather than caching, so no remember is claimed that does not happen.

Platform detection:

• Android: PackageManager.FEATURE_AUTOMOTIVE for car and FEATURE_SENSOR_HINGE_ANGLE for foldable, both behind SDK_INT guards (minSdk 23), plus the platform's own sw600dp tablet qualifier. The foldable check is documented as a heuristic, since without a Jetpack WindowManager dependency the hinge angle sensor is the only signal the platform exposes.
• Desktop: constant Desktop form factor, size class from LocalWindowInfo so it tracks window resizes.
• iOS: UIDevice.userInterfaceIdiom mapped to Phone/Tablet/Car, size class read from the window rather than the screen so it stays correct under iPad Split View and Stage Manager.

Validation: compileAndroidMain, compileKotlinDesktop, compileKotlinIosArm64 and compileKotlinIosSimulatorArm64 all pass.