Add transaction builder undo/redo stack

[Just-Bamford]

Problem

Building complex transactions, users can't easily undo/redo operations. No history tracking.

Solution

Implement transaction builder with history: \createTransactionBuilder()\ returns builder with \undo(),
edo()\ methods. Tracks operation history.

Acceptance Criteria

• Builder function added with undo/redo
• Tracks operation history
• Undo removes last operation
• Redo restores removed operation
• Tests cover undo/redo workflows

Note for contributors

Store history in closure. Reference builder pattern. Add tests to \src/tests/transaction.test.ts.