Refactor FXIOS-14485 FXIOS-14472 [Swift 6 Migration] Turn on Swift 6 at the Project Level, as well as Client and ClientTest targets

[tomerqodo]

Benchmark PR from qodo-benchmark#218

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Note

Swift 6 migration and concurrency safety

• Sets SWIFT_VERSION = 6.0 across project and test targets
• Adds @MainActor/@Sendable to numerous callbacks and delegate completion handlers (OnboardingFlowViewModel, OnboardingService, web view delegates, context menu actions, tab provider, autofill accessory, download toast)
• Wraps onboarding handleAction in a Task in LaunchCoordinator to align with actor isolation

Minor UI/behavior adjustments

• Hardcodes close button size in DownloadToast (removes local UX constant)
• Aligns closure types in BrowserWebController helpers and WebContextMenuActionsProvider for thread-safe tab operations

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Cursor Bugbot has reviewed your changes and found 2 potential issues.

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Inconsistent @Sendable removal from completion handler

Low Severity

The @Sendable annotation was removed from the completionHandler parameter in runJavaScriptAlertPanelWithMessage, but was kept on the similar runJavaScriptConfirmPanelWithMessage and runJavaScriptTextInputPanelWithPrompt methods in the same file (lines 56 and 71). This creates an inconsistency within the file and mismatches the corresponding implementation in BrowserViewController+WebViewDelegates.swift where all three methods have @Sendable on their completion handlers.

 

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Missing @Sendable on completion handler type creates mismatch

Medium Severity

The onActionTap closure's completion handler type in OnboardingFlowViewModel was updated to @MainActor @escaping (Result<TabAction, Error>) -> Void but is missing @Sendable. However, OnboardingService.handleAction expects @Sendable @escaping @MainActor (...) on its completion parameter. When completion is passed from the onActionTap closure in LaunchCoordinator to handleAction, there's a type mismatch since the closure typed without @Sendable is being passed where @Sendable is required.

Additional Locations (1)

• firefox-ios/Client/Frontend/Onboarding/Protocols/OnboardingService.swift#L64-L67