chore: Project cleanup and Canvas UX improvements (Phase 7-9)

## Cleanup (v0.5.0)
- Delete 102+ orphaned MCP session temp files
- Remove build artifacts (htmlcov, dist, __pycache__)
- Archive superseded plan docs (RALPH_LOOP V2/V3, CANVAS V3, etc.)
- Move debug/analysis scripts from tests/ to tools/analysis/
- Archive redundant NX journals to archive/nx_journals/
- Archive monolithic PROTOCOL.md to docs/archive/
- Update .gitignore with missing patterns
- Clean old study files (optimization_log_old.txt, run_optimization_old.py)

## Canvas UX (Phases 7-9)
- Phase 7: Resizable panels with localStorage persistence
  - Left sidebar: 200-400px, Right panel: 280-600px
  - New useResizablePanel hook and ResizeHandle component
- Phase 8: Enable all palette items
  - All 8 node types now draggable
  - Singleton logic for model/solver/algorithm/surrogate
- Phase 9: Solver configuration
  - Add SolverEngine type (nxnastran, mscnastran, python, etc.)
  - Add NastranSolutionType (SOL101-SOL200)
  - Engine/solution dropdowns in config panel
  - Python script path support

## Documentation
- Update CHANGELOG.md with recent versions
- Update docs/00_INDEX.md
- Create examples/README.md
- Add docs/plans/CANVAS_UX_IMPROVEMENTS.md

.gitignore

@@ -110,5 +110,17 @@ _dat_run*.dat
 .claude-mcp-*.json
 .claude-prompt-*.md
 
+# Backend logs
+backend_stdout.log
+backend_stderr.log
+*.log.bak
+
+# Linter/formatter caches
+.ruff_cache/
+.mypy_cache/
+
 # Auto-generated documentation (regenerate with: python -m optimization_engine.auto_doc all)
 docs/generated/
+
+# Malformed filenames (Windows path used as filename)
+C:*