chore: cleanup development artifacts and improve gitignore

Remove development artifacts and temporary files that accumulated during
the memory system unification work.

Changes:
- Remove backup files (*.bak) that were left from refactoring
- Remove macOS system files (.DS_Store)
- Remove IDE configuration files (.cursor/, .cursorignore)
- Remove temporary development documentation:
  - docs/kani_fixes_applied.md (development notes)
  - docs/deprecated_memory_patterns_guide.md (outdated guide)
- Update .gitignore to prevent future accumulation of:
  - Backup files (*.bak, *.orig, *.backup, *~, *.tmp)
  - macOS system files (.DS_Store)
  - IDE configuration directories

This cleanup ensures the repository contains only production code and
relevant documentation while preventing future accumulation of
development artifacts.

Author: avrabe

.cursorignore

@@ -37,4 +37,12 @@ docs/source/implementation/source_requirements.rst
 docs_artifact_final/
 docs_output/
 
+# Development artifacts
 *.bak*
+*.orig
+*.backup
+*~
+*.tmp
+.DS_Store
+.cursor/
+.cursorignore