docs(mobile/4): iOS build requires Xcode 26 (iOS 26 SDK)

[LukeTowers]

What

Updates the Mobile v4 → Getting Started → Environment Setup iOS requirements from Xcode 16.0 or later to Xcode 26 or later (and notes the implied macOS 15.6+).

Why

Building a fresh v4 app on Xcode 16.4 (iOS 18.5 SDK) fails to compile in NativePHP's own renderer:

nativephp/ios/NativePHP/NativeRender/NativeRootTabsRenderer.swift:909
error: value of type 'TabBarAccessoryModifier.Content' has no member 'tabViewBottomAccessory'

tabViewBottomAccessory is an iOS 26-only SwiftUI API. Because the symbol must exist in the SDK at compile time, an #available guard can't rescue an older SDK — the iOS 26 SDK (shipped with Xcode 26) is required. Xcode 26 in turn requires macOS 15.6+.

Reproduced with nativephp/mobile 4.0.1 / nativephp/mobile-ui 0.3.0 via php artisan native:run ios.

Note for maintainers

I documented this as the current requirement, but if the intent is to keep supporting Xcode 16, the alternative is to gate the iOS 26 API in the renderer (compile-time SDK check) rather than change the docs — happy to adjust this PR either way.

Changes

• resources/views/docs/mobile/4/getting-started/environment-setup.md: iOS requirements → Xcode 26 / macOS 15.6+, with a one-line rationale.

[LukeTowers]

Build log excerpt (reproduces the Xcode 16 failure)

Environment: Xcode 16.4 (Build 16F6), macOS 15.5, Apple silicon · nativephp/mobile 4.0.1 / mobile-ui 0.3.0 · php artisan native:run ios <ipad-sim-udid> --build=debug.

The active SDK is iOS 18.5 (the newest Xcode 16.4 ships), and that's where the compile dies:

xcodebuild output (key lines; full log is ~1900 lines of build-system noise)

# --- SDK / target (from build settings) ---
SDKROOT = iphonesimulator18.5
-target arm64-apple-ios18.2-simulator ...
  -isysroot .../Developer/SDKs/iPhoneSimulator18.5.sdk

# --- compile error ---
.../NativePHP/NativeRender/NativeRootTabsRenderer.swift:844:10: warning:
  'onChange(of:perform:)' was deprecated in iOS 17.0: Use `onChange` with a
  two or zero parameter action closure instead.
        .onChange(of: mode) { _ in
         ^
.../NativePHP/NativeRender/NativeRootTabsRenderer.swift:909:22: error:
  value of type 'TabBarAccessoryModifier.Content'
  (aka '_ViewModifier_Content<TabBarAccessoryModifier>')
  has no member 'tabViewBottomAccessory'
                    .tabViewBottomAccessory {
                     ^~~~~~~~~~~~~~~~~~~~~~

# --- failure tail ---
** BUILD FAILED **

The following build commands failed:
	SwiftCompile normal arm64 Compiling NativeRootTabsRenderer.swift, ... (in target 'NativePHP-simulator' from project 'NativePHP')
	SwiftCompile normal arm64 .../NativeRootTabsRenderer.swift (in target 'NativePHP-simulator' from project 'NativePHP')
	Building workspace NativePHP with scheme NativePHP-simulator
(3 failures)

tabViewBottomAccessory doesn't exist in the iOS 18.5 SDK, so the compiler rejects it outright — confirming an iOS 26 SDK (Xcode 26) is required to build the current release. Installing Xcode 26 (macOS 15.6+) is the fix.

(Full raw log withheld — it's ~272 KB of a private repo's build output; happy to share more specific sections if useful.)

[simonhamp]

Good find! I think we should actually make it so that tabViewBottomAccessory isn't attempted on anything pre-iOS 26