refactor: replace AnyChangeManager closure erasure with ChangeManaging protocol

[datlechin]

Summary

• AnyChangeManager was a closure-based type erasure class with 7 @ObservationIgnored closure properties and changes: [Any] forcing as? RowChange runtime downcasts
• Now uses a ChangeManaging protocol that both DataChangeManager and StructureChangeManager conform to
• AnyChangeManager is a thin @Observable wrapper with a single wrapped: any ChangeManaging property
• changes: [Any] replaced with typed rowChanges: [RowChange]
• All as? RowChange downcasts eliminated (2 call sites in DataGridCoordinator + DataGridView)
• Net -34 lines (71 added, 105 removed)

Test plan

• Edit cells in data tab — verify changes tracked and displayed (colored rows)
• Undo/redo edits — verify works
• Save changes — verify SQL generated correctly
• Structure tab — verify column/index/FK changes tracked
• Structure tab undo/redo — verify works
• Create table — verify change manager works
• Switch between data and structure tabs — verify no cross-contamination

[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Update test-facing AnyChangeManager API changes

This refactor removes the labeled initializers in favor of init(_:) (and also renames the exposed change list to rowChanges), but the existing test target still calls AnyChangeManager(dataManager:), AnyChangeManager(structureManager:), and wrapper.changes in TableProTests/Core/ChangeTracking/AnyChangeManagerTests.swift. In environments that build tests (CI/local test runs), this change set will fail to compile until those call sites are updated or compatibility shims are kept.

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