Add aiyagari_egm to table of contents

- Added aiyagari_egm.md to _toc.yml
- Placed directly after aiyagari.md in Multiple Agent Models section

Author: claude

lectures/_toc.yml

@@ -107,6 +107,7 @@ parts:
   - file: markov_perf
   - file: uncertainty_traps
   - file: aiyagari
+  - file: aiyagari_egm
   - file: ak_aiyagari
 - caption: Asset Pricing and Finance
   numbered: true