[D12] SA Verify + Methodology Notes Update

[Siddardth7]

Due: April 7 | Day 12 of 14

• Document SA spot-check results in docs/Methodology_Notes.md — table of CLT vs FEA ranks
• Add CalculiX setup section to Methodology Notes (install, .inp format, output parsing)
• Add Hashin criteria section — explain all 4 modes + Hashin-Rotem simplification used
• Search all .py files for TODO — resolve every remaining stub
• Confirm compare_clt_fea.py has no placeholder code

✅ Done when: Methodology Notes updated. grep -r "TODO" src/ returns nothing critical.