feat(06-04): implement --simulate dry-run mode

- Added simulate mode check before download loop
- When --simulate is set, prints URLs that would be downloaded but skips actual download
- Added destination directory creation if it doesn't exist
- Uses --destination argument for download location

src/main.rs

@@ -195,7 +195,7 @@ fn main() {
                     // Create a simple destination path based on the URL
                     // In a full implementation, this would use path templates
                     let filename = format!("{}.download", j + 1);
-                    let destination = PathBuf::from(".").join(&filename);
+                    let destination = args.destination.clone().unwrap_or_else(|| PathBuf::from(".")).join(&filename);
                     
                     let mut values = HashMap::new();
                     values.insert("num".to_string(), serde_json::json!(j + 1));
@@ -212,6 +212,27 @@ fn main() {
                 }
                 total_items += items.len();
                 
+                // Check for simulate/dry-run mode
+                if args.simulate {
+                    log::info!("SIMULATE MODE: URLs extracted but not downloaded");
+                    // Still print what would be downloaded
+                    for item in &download_items {
+                        println!("[SIMULATE] Would download: {} -> {:?}", item.url, item.destination);
+                    }
+                    continue; // Skip actual download
+                }
+                
+                // Ensure destination directory exists
+                if let Some(ref dest) = args.destination {
+                    if !dest.exists() {
+                        if let Err(e) = std::fs::create_dir_all(dest) {
+                            log::warn!("Failed to create destination directory {:?}: {}", dest, e);
+                        } else {
+                            log::info!("Created destination directory: {:?}", dest);
+                        }
+                    }
+                }
+                
                 // Actually download the files using DownloadWorker
                 if !download_items.is_empty() {
                     let worker = match DownloadWorker::new(jobs) {