feat: support ios 16 for swiftui

[Yash-Singh1]

Clerk iOS fork is at https://github.com/Yash-Singh1/clerk-ios/tree/backport-clerkkitui-auth-ios16

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Note

Medium Risk
Navigation and observation plumbing change across the whole app (split view vs stack, Combine vs Observation). Clerk is pinned to a fork revision, so auth UI on 16.x needs extra verification.

Overview
Lowers the native SwiftUI app (and extensions) from iOS 17 to 16.2, replacing Observation/@Bindable with Combine ObservableObject/@Published and @ObservedObject/@StateObject.

Adds iOS 16 shims in T3Theme (T3ContentUnavailableView, t3OnChange, presentation/list/scroll helpers) and uses them across empty states and change handlers. Compact WorkspaceView falls back to NavigationStack on iOS 16; widgets, markdown link taps, Clerk env injection, and terminal trait updates get version-gated paths.

Pins Clerk to a fork revision that supports iOS 16. Tests wait on $Published publishers instead of withObservationTracking.

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Note

Add iOS 16 support by migrating to Combine and back-deploying SwiftUI APIs

• Lowers IPHONEOS_DEPLOYMENT_TARGET from 17.0 to 16.2 and updates the Clerk dependency to a pinned revision from a new repository.
• Migrates view models and views from Swift Observation (@Observable, @Bindable) to Combine (ObservableObject, @Published, @StateObject, @ObservedObject).
• Introduces T3ContentUnavailableView and modifiers like .t3OnChange, .t3PresentationBackground, and .t3ScrollBounceBasedOnSize to provide iOS 16 fallbacks for iOS 17 APIs.
• Reworks WorkspaceView navigation to use NavigationStack with isPresented bindings on iOS 16 compact layouts instead of NavigationSplitView.
• Risk: The Clerk dependency change in T3Code.xcodeproj/project.pbxproj switches to a new repository at a pinned revision; verify the revision contains the expected symbols and does not introduce regressions.

^{Macroscope summarized bd75a77.}

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[github-actions]

Thread transfer impact

✅ Thread transfer remains within every enforced ceiling.

ℹ️ No successful main baseline artifact is available yet. This run establishes the initial measurement.

Provider	Metric	Main baseline	This PR	Impact	PR ceiling
Codex	Total thread wire	—	12.6 KiB	—	15.1 KiB	✅
Codex	Thread snapshot wire	—	6.3 KiB	—	7.3 KiB	✅
Codex	Live turn WebSocket wire	—	6.3 KiB	—	7.8 KiB	✅
Codex	Live turn WebSocket decoded	—	51.8 KiB	—	66.4 KiB	✅
Codex	Live turn messages	—	16	—	21	✅
Claude	Total thread wire	—	12.6 KiB	—	15.1 KiB	✅
Claude	Thread snapshot wire	—	6.3 KiB	—	7.3 KiB	✅
Claude	Live turn WebSocket wire	—	6.3 KiB	—	7.8 KiB	✅
Claude	Live turn WebSocket decoded	—	52.7 KiB	—	66.4 KiB	✅
Claude	Live turn messages	—	16	—	21	✅

Baseline: unavailable · PR result: bd75a77 · Source CI: success

Scenario and decoded snapshot size

10 historical turns, 5 command tools per turn, 878.9 KiB retained MCP result per historical turn, and a 1.05 MiB retained result in the measured turn.

• Codex decoded thread snapshot: 99.9 KiB
• Claude decoded thread snapshot: 100.6 KiB

Updated in place by a trusted workflow. PR artifacts are strictly validated and never executed.

[cursor]

Cursor Bugbot has reviewed your changes using high effort and found 1 potential issue.

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[macroscopeapp]

Approvability

Verdict: Not approved

Macroscope's review found this PR not approvable — This PR is a broad iOS 16 compatibility feature with new navigation, observation, UI fallback, widget, and dependency behavior rather than a low-risk maintenance change. The new compact-navigation path has an unresolved transition defect, and the Clerk package is switched to a personal fork, so the runtime and dependency changes need human review.

Notes:

• No code objects were reviewed. Approvability was decided on eligibility alone.

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