Fix 12 medium-severity bugs across all crates

- Escape backslashes in Nautilus preset names preventing Python injection
- Fix tiled watermarks starting at (spacing,spacing) instead of (0,0)
- Fix text watermark width overestimation (1.0x to 0.6x multiplier)
- Fix output_dpi forcing re-encoding for metadata-only presets
- Fix AVIF/WebP compression detection comparing against wrong preset values
- Add shared batch_updating guard for Ctrl+A/Ctrl+Shift+A select actions
- Fix overwrite conflict check ignoring preserve_directory_structure
- Add changes_filename()/changes_extension() for smarter overwrite checks
- Fix watch folder hardcoding "Blog Photos" preset
- Fix undo dropping history for partially-trashed batches
- Fix skipped files inflating size statistics
- Make CLI watch config writes atomic

pixstrip-cli/src/main.rs

@@ -573,25 +573,27 @@ fn cmd_undo(count: usize) {
                     entry.total, entry.input_dir
                 );
 
-                let mut batch_trashed = 0;
+                let mut remaining_files = Vec::new();
                 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) => {
                                 eprintln!("  Failed to trash {}: {}", path.display(), e);
+                                remaining_files.push(file_path.clone());
                             }
                         }
                     }
                 }
 
-                // Keep entry in history if no files were trashed
-                if batch_trashed == 0 {
-                    failed_entries.push(entry);
+                // Keep entry with remaining files if some could not be trashed
+                if !remaining_files.is_empty() {
+                    let mut kept = entry;
+                    kept.output_files = remaining_files;
+                    failed_entries.push(kept);
                 }
             }
 
@@ -665,7 +667,7 @@ fn cmd_watch_add(path: &str, preset_name: &str, recursive: bool) {
     }
     match serde_json::to_string_pretty(&watches) {
         Ok(json) => {
-            if let Err(e) = std::fs::write(&watches_path, json) {
+            if let Err(e) = pixstrip_core::storage::atomic_write(&watches_path, &json) {
                 eprintln!("Failed to write watch config: {}", e);
                 std::process::exit(1);
             }
@@ -743,7 +745,7 @@ fn cmd_watch_remove(path: &str) {
 
     match serde_json::to_string_pretty(&watches) {
         Ok(json) => {
-            if let Err(e) = std::fs::write(&watches_path, json) {
+            if let Err(e) = pixstrip_core::storage::atomic_write(&watches_path, &json) {
                 eprintln!("Failed to write watch config: {}", e);
                 std::process::exit(1);
             }