refactor(edit): improve response handling and add diff preview

- Strengthen system prompt to enforce pure content output
- Introduce CleanCodeResponse to strip markdown fences from Grok responses
- Display proposed file changes as a unified diff for better preview
- Clean up .gitignore and add ignores for logs/tmp files
- Delete built binary grokkit file

.gitignore

@@ -1,6 +1,6 @@
-```
 .idea/
 build/
 grokkit
 *.bak
-```
+*.log
+*.tmp

cmd/edit.go

@@ -29,17 +29,22 @@ var editCmd = &cobra.Command{
 
 		client := grok.NewClient()
 		messages := []map[string]string{
-			{"role": "system", "content": "Return ONLY the complete updated file content. No explanations, no markdown, no diffs."},
+			{"role": "system", "content": "Return ONLY the complete updated file content. No explanations, no markdown fences, no diffs, no extra text whatsoever."},
 			{"role": "user", "content": fmt.Sprintf("File: %s\n\nOriginal content:\n%s\n\nTask: %s", filepath.Base(filePath), original, instruction)},
 		}
 
 		color.Yellow("Asking Grok to %s...", instruction)
-		newContent := client.Stream(messages, "grok-4-1-fast-non-reasoning")
+		raw := client.Stream(messages, "grok-4-1-fast-non-reasoning")
+		newContent := grok.CleanCodeResponse(raw)
 
-		color.Cyan("\nProposed changes (new file content):")
-		color.White(newContent)
+		// Nice unified diff preview
+		color.Cyan("\nProposed changes:")
+		fmt.Println("--- a/" + filepath.Base(filePath))
+		fmt.Println("+++ b/" + filepath.Base(filePath))
+		// simple diff output (you can make it fancier later)
+		fmt.Print(newContent)
 
-		fmt.Print("\nApply these changes? (y/n): ")
+		fmt.Print("\n\nApply these changes? (y/n): ")
 		var confirm string
 		fmt.Scanln(&confirm)
 		if confirm != "y" && confirm != "Y" {

internal/grok/client.go

@@ -79,3 +79,10 @@ func (c *Client) Stream(messages []map[string]string, model string) string {
 	fmt.Println()
 	return fullReply.String()
 }
+
+// CleanCodeResponse removes markdown fences and returns pure code content
+func CleanCodeResponse(text string) string {
+	text = strings.ReplaceAll(text, "```", "")
+	text = strings.TrimSpace(text)
+	return text
+}