Add Go line length guidelines

Adds 120/100/80 character guidelines to AGENTS.md

AGENTS.md

@@ -2,13 +2,14 @@
 
 ## Skills: Always Active
 
-At the start of every conversation, load the following skills using the `skill` tool before responding to the user:
+At the start of every conversation, load the following skills using the `skill`
+tool before responding to the user:
 
 1. **caveman** — Always use caveman mode (full intensity) for all responses
 
 ## Code Organization
 
-### Go file structure
+### Go: File Structure
 - Public (exported) functions must appear at the top of each file.
 - Private (unexported) functions must appear at the bottom of each file.
 - Within each section, functions must be sorted alphabetically by function name.
@@ -16,3 +17,12 @@ At the start of every conversation, load the following skills using the `skill`
 
 	// -----------------------------------------
 	// private
+
+### Go: Line Length
+
+Keep Go lines as short as reasonably possible.
+
+- **Hard limit:** 120 characters — never exceed this.
+- **Preferred:** 100 characters or fewer in normal cases.
+- **Target:** 80 characters if breaking the line produces cleaner, more readable
+  code (e.g. chained calls, long argument lists, multi-condition `if` statements).