* fix: undo() peeks without popping, breaking repeated undo and leaking redo stack
undo() used self.undo_stack.back() (peek) instead of pop_back(), so
repeated undo always returned the same checkpoint while pushing to
the redo stack unboundedly.
Additionally, redo() did not save the current state to the undo stack,
breaking the undo/redo cycle.
Changes:
- undo(): change back() to pop_back(), return owned Checkpoint
- redo(): accept current_turn/current_messages params, save current
state to undo stack before popping from redo stack
- Update process_undo/process_redo callers in agent_loop.rs
- Add tests for repeated undo, undo/redo cycling, stack size invariant
* fix: standardize lock ordering and extract push_undo helper
Address review feedback:
- Standardize lock order (Session before UndoManager) in process_undo
and process_redo to match process_user_input and prevent deadlocks
- Extract push_undo() helper to deduplicate push-and-trim logic shared
by checkpoint() and redo()
* docs: add move-semantics notes and stack invariant to UndoManager
Address review feedback requesting documentation about the ownership
semantics of undo/redo parameters and the stack size invariant.
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Co-authored-by: Yi LIU <[email protected]>
Co-authored-by: firat.sertgoz <[email protected]>
