feat: add Go extract_script_description function

Funcion Go pura del dominio shell que extrae la descripcion de un script Bash
parseando el header del archivo. Busca comentarios con formato estandar y
retorna la primera linea de descripcion encontrada. Util para indexar scripts
automaticamente.

functions/shell/extract_script_description.go

@@ -0,0 +1,48 @@
+package shell
+
+import (
+	"bufio"
+	"os"
+	"path/filepath"
+	"strings"
+)
+
+// ExtractScriptDescription parses a script file and returns the first
+// meaningful comment line as a description. Skips shebangs and empty lines.
+// Falls back to the filename (without extension, underscores replaced by spaces).
+func ExtractScriptDescription(scriptPath string) string {
+	file, err := os.Open(scriptPath)
+	if err != nil {
+		return fallbackDescription(scriptPath)
+	}
+	defer file.Close()
+
+	scanner := bufio.NewScanner(file)
+	lineCount := 0
+	for scanner.Scan() && lineCount < 5 {
+		line := strings.TrimSpace(scanner.Text())
+		lineCount++
+
+		if strings.HasPrefix(line, "#!") || line == "" {
+			continue
+		}
+		if strings.HasPrefix(line, "#") {
+			desc := strings.TrimSpace(strings.TrimPrefix(line, "#"))
+			desc = strings.TrimSpace(strings.TrimPrefix(desc, "Script:"))
+			desc = strings.TrimSpace(strings.TrimPrefix(desc, "Script para"))
+			desc = strings.TrimSpace(strings.TrimPrefix(desc, "Descripción:"))
+			desc = strings.TrimSpace(strings.TrimPrefix(desc, "Description:"))
+			if desc != "" {
+				return desc
+			}
+		}
+	}
+
+	return fallbackDescription(scriptPath)
+}
+
+func fallbackDescription(scriptPath string) string {
+	name := filepath.Base(scriptPath)
+	name = strings.TrimSuffix(name, filepath.Ext(name))
+	return strings.ReplaceAll(name, "_", " ")
+}