chore: update analyze command output and add Rexx to linter

- Change default output filename in analyze command from analyze.md to analysis.md
- Add Rexx language detection with extensions .rx, .rex, .rexlib, .rexx, .cls

cmd/analyze.go

@@ -30,7 +30,7 @@ Uses language-specific prompts discovered in .grokkit/prompts/ or ~/.config/grok
 		}
 		output := viper.GetString("output")
 		if output == "" {
-			output = "analyze.md"
+			output = "analysis.md"
 		}
 		// Fixed: config.GetModel takes (commandName, flagModel)
 		model := config.GetModel("analyze", viper.GetString("model"))

internal/linter/linter.go

@@ -170,6 +170,10 @@ var languages = []Language{
 			},
 		},
 	},
+	{
+		Name:       "Rexx",
+		Extensions: []string{".rx", ".rex", ".rexlib", ".rexx", ".cls"},
+	},
 }
 
 // DetectLanguage detects the programming language based on file extension