work needed for adding coin 3 and coin 4 inputs (#31)

Author: mogorman

AGENTS.md

@@ -235,7 +235,7 @@ result, err := parser.EvalExpressions(envStruct)
 - **System**: `execute`, `delay`, `evaluate`, `stop`, `echo`
 - **MiSTer**: `mister.ini`, `mister.core`, `mister.script`, `mister.mgl`
 - **HTTP**: `http.get`, `http.post`
-- **Input**: `input.keyboard`, `input.gamepad`, `input.coinp1`, `input.coinp2`
+- **Input**: `input.keyboard`, `input.gamepad`, `input.coinp1`, `input.coinp2`, `input.coinp3`, `input.coinp4`
 - **UI**: `ui.notice`, `ui.picker`
 - **Metadata**: `traits` (parsed from `#key=value` syntax)
 

models.go

@@ -56,6 +56,8 @@ const (
 	ZapScriptCmdInputGamepad  = "input.gamepad"
 	ZapScriptCmdInputCoinP1   = "input.coinp1"
 	ZapScriptCmdInputCoinP2   = "input.coinp2"
+	ZapScriptCmdInputCoinP3   = "input.coinp3"
+	ZapScriptCmdInputCoinP4   = "input.coinp4"
 
 	ZapScriptCmdUINotice = "ui.notice"
 	ZapScriptCmdUIPicker = "ui.picker"