feat: Implement Mastra API routes, add chat sidebar component, and document Next.js API routes with streaming patterns.

Author: ssdeanx

.gitignore

@@ -158,3 +158,7 @@ thoughts/ledgers/CONTINUITY_ses_3944.md
 .gitmodules
 thoughts/ledgers/CONTINUITY_ses_38c6.md
 thoughts/ledgers/CONTINUITY_ses_38e5.md
+thoughts/ledgers/CONTINUITY_ses_388a.md
+thoughts/ledgers/CONTINUITY_ses_3885.md
+thoughts/ledgers/CONTINUITY_ses_3886.md
+thoughts/ledgers/CONTINUITY_ses_3889.md