Clean up macOS leftovers and inline title helpers

[BugenZhao]

Summary

• remove unused macOS build leftovers and dead xargo configuration
• delete unreferenced macOS app sources and flatten remaining iOS-only branches
• inline navigation title and toolbar placement helpers into direct SwiftUI APIs

Verification

• xcodebuild -project app/MNGA.xcodeproj -scheme MNGA -sdk iphonesimulator -destination "platform=iOS Simulator,name=iPhone 17,OS=26.2" build CODE_SIGNING_ALLOWED=NO
• make swiftformat

[Copilot]

Pull request overview

Removes macOS platform support (build targets, source files, conditional compilation branches) and inlines helper wrappers (navigationTitleInline, navigationTitleLarge, mayNavigationBarTrailing, etc.) into direct SwiftUI API calls.

Changes:

• Delete all macOS-specific source files, entitlements, Info.plist, Xargo config, and commented-out Tuist target definition
• Remove #if os(macOS) / #if os(iOS) conditional branches throughout shared code, flattening to iOS-only paths
• Replace custom navigation title/toolbar placement helpers with direct SwiftUI APIs (.navigationTitle, .navigationBarTitleDisplayMode, .navigationBarTrailing)

Reviewed changes

Copilot reviewed 26 out of 26 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
logic/logic/Xargo.toml	Remove dead xargo (Catalyst) config
app/macOS/*	Delete all macOS source files
app/Project.swift	Remove commented-out macOS target
app/Shared/Utilities/Platform.swift	Remove macOS branches, inline title/toolbar helpers; move copyToPasteboard into View extension
app/Shared/Views/*.swift	Replace helper calls with direct SwiftUI APIs
app/Shared/MNGAApp.swift	Remove macOS Settings scene and flatten #if
Makefile	Remove macOS/Catalyst build targets and cargo-lipo
README.md	Update feature description and build instructions

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