Fix 5 high-risk bugs from 13th audit pass

- cleanup_placeholder now removes 1-byte marker files on error (regression)
- {width}/{height} template vars replaced with "0" when dimensions unavailable
- Text watermark width multiplier 0.6->1.0 to prevent CJK/wide char clipping
- cmd_undo preserves history entries when trash operations fail
- cmd_watch_remove exits on write failure instead of silent discard

pixstrip-cli/src/main.rs

@@ -535,13 +535,15 @@ fn cmd_undo(count: usize) {
             let undo_count = count.min(entries.len());
             let to_undo = entries.split_off(entries.len() - undo_count);
             let mut total_trashed = 0;
+            let mut failed_entries = Vec::new();
 
-            for entry in &to_undo {
+            for entry in to_undo {
                 if entry.output_files.is_empty() {
                     println!(
                         "Batch from {} has no recorded output files - cannot undo",
                         entry.timestamp
                     );
+                    failed_entries.push(entry);
                     continue;
                 }
 
@@ -550,11 +552,13 @@ fn cmd_undo(count: usize) {
                     entry.total, entry.input_dir
                 );
 
+                let mut batch_trashed = 0;
                 for file_path in &entry.output_files {
                     let path = PathBuf::from(file_path);
                     if path.exists() {
                         match trash::delete(&path) {
                             Ok(()) => {
+                                batch_trashed += 1;
                                 total_trashed += 1;
                             }
                             Err(e) => {
@@ -563,9 +567,17 @@ fn cmd_undo(count: usize) {
                         }
                     }
                 }
+
+                // Keep entry in history if no files were trashed
+                if batch_trashed == 0 {
+                    failed_entries.push(entry);
+                }
             }
 
-            // Remove undone entries from history
+            // Re-add entries where trash failed so they can be retried
+            entries.extend(failed_entries);
+
+            // Write updated history
             if let Err(e) = history.write_all(&entries) {
                 eprintln!("Warning: failed to update history after undo: {}", e);
             }
@@ -706,8 +718,17 @@ fn cmd_watch_remove(path: &str) {
         return;
     }
 
-    if let Ok(json) = serde_json::to_string_pretty(&watches) {
-        let _ = std::fs::write(&watches_path, json);
+    match serde_json::to_string_pretty(&watches) {
+        Ok(json) => {
+            if let Err(e) = std::fs::write(&watches_path, json) {
+                eprintln!("Failed to write watch config: {}", e);
+                std::process::exit(1);
+            }
+        }
+        Err(e) => {
+            eprintln!("Failed to serialize watch config: {}", e);
+            std::process::exit(1);
+        }
     }
     println!("Removed watch folder: {}", path);
 }