Add defensive validation to detect and prevent cycles in the session tree
parent chain that could occur after compaction or file corruption.
- Add tree_validation.go with cycle detection and parent chain validation
- Validate parent chain before appending messages (AppendMessage)
- Validate firstKeptEntryID exists in AppendCompaction
- Add depth limit and cycle detection to buildTreeNode to prevent infinite recursion
- Log diagnostics on session open to detect existing cycles
- Add tests for cycle detection and graceful handling
Ed Zynda