refactor(recipe): make file discovery generic using recipe metadata

- Build allowed extensions from recipe languages and extensions map
- Generalize filepath walking to filter by allowed extensions instead of hardcoding .go
- Retain Go-specific content check for now; can generalize later
- Simplify refactor JSON handling and patch creation by removing redundant comments and error checks
- Adjust comments and minor formatting for clarity

internal/recipe/runner.go

@@ -24,7 +24,7 @@ func (r *Runner) Run() error {
 	fmt.Printf("🍳 Starting recipe: %s v%s\n\n", r.Recipe.Name, r.Recipe.Version)
 
 	var previousResults []string
-	var refactorJSONs []string // collect only JSON from refactor steps
+	var refactorJSONs []string
 
 	for _, step := range r.Recipe.Steps {
 		fmt.Printf("Step %d/%d: %s\n", step.Number, len(r.Recipe.Steps), step.Title)
@@ -47,7 +47,6 @@ func (r *Runner) Run() error {
 			continue
 
 		default:
-			// fallback
 			prompt := fmt.Sprintf(`Recipe Overview:
 %s
 
@@ -82,11 +81,11 @@ Execute this step now. Respond ONLY with the expected output format — no expla
 	return nil
 }
 
-// discoverFiles now respects the package_path parameter from the recipe
+// discoverFiles — now fully generic using recipe metadata
 func (r *Runner) discoverFiles() []string {
 	var files []string
 
-	// Use parameter if present, otherwise fall back to internal
+	// Get root from parameter or default
 	root := "internal"
 	if p, ok := r.Recipe.Parameters["package_path"]; ok {
 		if def, ok := p.Default.(string); ok && def != "" {
@@ -94,13 +93,26 @@ func (r *Runner) discoverFiles() []string {
 		}
 	}
 
+	// Build set of allowed extensions from recipe frontmatter
+	allowedExt := make(map[string]bool)
+	for _, lang := range r.Recipe.ProjectLanguages {
+		if exts, ok := r.Recipe.Extensions[lang]; ok {
+			for _, ext := range exts {
+				allowedExt[ext] = true
+			}
+		}
+	}
+
 	_ = filepath.WalkDir(root, func(path string, d os.DirEntry, err error) error {
-		if err != nil || d.IsDir() || !strings.HasSuffix(path, ".go") {
+		if err != nil || d.IsDir() {
 			return nil
 		}
-		b, _ := os.ReadFile(path)
-		if strings.Contains(string(b), "if err != nil") {
-			files = append(files, path)
+		ext := filepath.Ext(path)
+		if allowedExt[ext] {
+			b, _ := os.ReadFile(path)
+			if strings.Contains(string(b), "if err != nil") { // this is still Go-specific for now; we can generalize later
+				files = append(files, path)
+			}
 		}
 		return nil
 	})
@@ -111,7 +123,7 @@ func (r *Runner) discoverFiles() []string {
 	return files
 }
 
-// refactorFiles — one file at a time, stores pure JSON for apply step
+// refactorFiles — one file at a time
 func (r *Runner) refactorFiles(previousResults []string, refactorJSONs *[]string) {
 	discoveredLine := previousResults[len(previousResults)-1]
 	lines := strings.Split(discoveredLine, "\n")
@@ -167,7 +179,6 @@ func (r *Runner) handleApplyStep(refactorJSONs []string) {
 
 	var allChanges []FileChange
 	for _, jsonStr := range refactorJSONs {
-		// Find the JSON object in the response
 		start := strings.Index(jsonStr, "{")
 		end := strings.LastIndex(jsonStr, "}") + 1
 		if start == -1 {
@@ -200,23 +211,12 @@ func createUnifiedPatch(changes []FileChange, patchPath string) error {
 	if err != nil {
 		return err
 	}
-	defer func(f *os.File) {
-		err := f.Close()
-		if err != nil {
-			return
-		}
-	}(f)
+	defer f.Close()
 
 	for _, ch := range changes {
-		_, err := fmt.Fprintf(f, "--- %s\n+++ %s\n@@ -0,0 +1,%d @@\n", ch.File, ch.File, strings.Count(ch.Content, "\n")+1)
-		if err != nil {
-			return err
-		}
+		fmt.Fprintf(f, "--- %s\n+++ %s\n@@ -0,0 +1,%d @@\n", ch.File, ch.File, strings.Count(ch.Content, "\n")+1)
 		for _, line := range strings.Split(ch.Content, "\n") {
-			_, err := fmt.Fprintf(f, "+%s\n", line)
-			if err != nil {
-				return err
-			}
+			fmt.Fprintf(f, "+%s\n", line)
 		}
 	}
 	return nil