add rgb check and example

AGENTS.md

@@ -1,5 +1,7 @@
 # AGENTS
 
+ALWAYS COMPACT YOUR CONTEXT FIRST!
+
 ## Map
 
 - Root has workspace files.
@@ -43,6 +45,7 @@
 - Short names.
 - Short comments.
 - Explain embedded idea.
+- Every Rust function we write except the main must have a short description header comment following rust best practice
 - Do not explain obvious Rust syntax.
 - No heap.
 - No dynamic dispatch unless teaching needs it.