ci (AGENTS.md): add llm instructions

- AGENTS.md: generated with claude + serena mcp
- settings.json: claude-specific permissions
- .gitignore: add exclusions/inclusions

Closes #779

.gitignore

@@ -1,5 +1,7 @@
 # ETC
 *.out
+.serena/
+CLAUDE.md
 
 # Byte-compiled / optimized / DLL files
 __pycache__/
@@ -292,3 +294,8 @@ dist
 .yarn/build-state.yml
 .yarn/install-state.gz
 .pnp.*
+
+# INCLUDE
+!**/.gitkeep
+!**/*.example
+!**/AGENTS.md