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-core/src/executor.rs

@@ -723,10 +723,11 @@ fn paths_are_same(a: &std::path::Path, b: &std::path::Path) -> bool {
     }
 }
 
-/// Remove a 0-byte placeholder file created by find_unique_path on error.
+/// Remove a placeholder file created by find_unique_path on error.
+/// Placeholders are either 0-byte (no marker) or 1-byte (marker `~`).
 fn cleanup_placeholder(path: &std::path::Path) {
     if let Ok(meta) = std::fs::metadata(path) {
-        if meta.len() == 0 {
+        if meta.len() <= 1 {
             let _ = std::fs::remove_file(path);
         }
     }

pixstrip-core/src/operations/rename.rs

@@ -40,9 +40,15 @@ pub fn apply_template_full(
         result = result.replace("{counter}", &counter.to_string());
     }
 
-    if let Some((w, h)) = dimensions {
-        result = result.replace("{width}", &w.to_string());
-        result = result.replace("{height}", &h.to_string());
+    match dimensions {
+        Some((w, h)) => {
+            result = result.replace("{width}", &w.to_string());
+            result = result.replace("{height}", &h.to_string());
+        }
+        None => {
+            result = result.replace("{width}", "0");
+            result = result.replace("{height}", "0");
+        }
     }
 
     // {date} - today's date

pixstrip-core/src/operations/watermark.rs

@@ -168,7 +168,7 @@ fn render_text_to_image(
     opacity: f32,
 ) -> image::RgbaImage {
     let scale = ab_glyph::PxScale::from(font_size);
-    let text_width = ((text.chars().count().min(10_000) as f32 * font_size.min(1000.0) * 0.6) as u32).saturating_add(4).min(8192);
+    let text_width = ((text.chars().count().min(10_000) as f32 * font_size.min(1000.0) * 1.0) as u32).saturating_add(4).min(16384);
     let text_height = ((font_size.min(1000.0) * 1.4) as u32).saturating_add(4).min(4096);
 
     let alpha = (opacity * 255.0).clamp(0.0, 255.0) as u8;
@@ -266,7 +266,7 @@ fn apply_text_watermark(
     } else {
         // No rotation - draw text directly (faster)
         let scale = ab_glyph::PxScale::from(font_size);
-        let text_width = ((text.chars().count().min(10_000) as f32 * font_size.min(1000.0) * 0.6) as u32).saturating_add(4).min(8192);
+        let text_width = ((text.chars().count().min(10_000) as f32 * font_size.min(1000.0) * 1.0) as u32).saturating_add(4).min(16384);
         let text_height = ((font_size.min(1000.0) * 1.4) as u32).saturating_add(4).min(4096);
         let text_dims = Dimensions {
             width: text_width,
@@ -336,7 +336,7 @@ fn apply_tiled_text_watermark(
         let alpha = (opacity * 255.0).clamp(0.0, 255.0) as u8;
         let draw_color = Rgba([color[0], color[1], color[2], alpha]);
 
-        let text_width = ((text.chars().count().min(10_000) as f32 * font_size.min(1000.0) * 0.6) as i64 + 4).min(8192);
+        let text_width = ((text.chars().count().min(10_000) as f32 * font_size.min(1000.0) * 1.0) as i64 + 4).min(16384);
         let text_height = ((font_size.min(1000.0) * 1.4) as i64 + 4).min(4096);
 
         let mut y = spacing as i64;