Reduce AnyView usage in PaneGridView to improve SwiftUI diffing

[2witstudios]

Problem

PaneGridView.swift wraps all nodes in AnyView to break the recursive opaque return type:

private func rootView(_ node: PaneSplitNode) -> AnyView { ... }
private func nodeView(_ node: PaneSplitNode) -> AnyView { ... }

AnyView defeats SwiftUI's structural diffing — it cannot efficiently compare old and new view trees, leading to full view hierarchy destruction/recreation on any change. For a grid of terminals, this means split ratio changes or focus changes can cause terminal views to be needlessly torn down and rebuilt.

Impact

• Terminal views may be destroyed and recreated unnecessarily when focus changes or splits are adjusted
• Animation transitions may not work correctly
• SwiftUI's identity tracking is broken for the entire grid subtree

Suggested approach

Options to explore:

1. Use @ViewBuilder with explicit conditional logic and stable view identities
2. Use Group with stable .id() values at the leaf level
3. Only type-erase at the leaf PaneCellView level, not the entire tree
4. Consider a custom layout container that doesn't require type erasure

This is a complex change since the recursive tree structure genuinely needs type erasure somewhere — the goal is minimizing its scope.

Files

• apps/purepoint-macos/purepoint-macos/Views/PaneGrid/PaneGridView.swift