refactor(panels): single-source the truncate-ellipsis helper

component_browser_panel, design_md_panel/helpers, git_panel, and
variables_panel/paint each defined their own char-aware truncate-with-ellipsis
fn (3 identical; variables used max-1 which could panic at 0). Hoist one
truncate_ellipsis into op-editor-ui::util and re-export under the original
name+visibility at each site, so the 9 git_panel call sites etc. stay
unchanged. The saturating bound also removes the variables-panel panic-at-0
latent bug.

crates/op-editor-ui/src/util.rs

@@ -157,10 +157,30 @@ pub fn resize_bounds(start: Rect, handle: SelectionHandle, dx: f32, dy: f32) ->
     Rect::xywh(x, y, w, h)
 }
 
+/// Truncate `s` to at most `max` characters, appending a `…` ellipsis when it
+/// is shortened (the ellipsis counts toward `max`). Character-aware, so
+/// multibyte glyphs are never split.
+pub fn truncate_ellipsis(s: &str, max: usize) -> String {
+    if s.chars().count() <= max {
+        return s.to_string();
+    }
+    let kept: String = s.chars().take(max.saturating_sub(1)).collect();
+    format!("{kept}…")
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
 
+    #[test]
+    fn truncate_ellipsis_appends_only_when_shortened() {
+        assert_eq!(truncate_ellipsis("hello", 10), "hello");
+        assert_eq!(truncate_ellipsis("hello", 5), "hello");
+        assert_eq!(truncate_ellipsis("hello", 3), "he…");
+        // Saturating: max == 0 must not panic.
+        assert_eq!(truncate_ellipsis("hello", 0), "…");
+    }
+
     #[test]
     fn parse_hex_expands_shorthand_and_zero_pads() {
         assert_eq!(

crates/op-editor-ui/src/widgets/component_browser_panel.rs

@@ -676,10 +676,4 @@ impl<'a> ComponentBrowserPanel<'a> {
     }
 }
 
-pub(in crate::widgets) fn truncate(s: &str, max: usize) -> String {
-    if s.chars().count() <= max {
-        return s.to_string();
-    }
-    let kept: String = s.chars().take(max.saturating_sub(1)).collect();
-    format!("{kept}…")
-}
+pub(in crate::widgets) use crate::util::truncate_ellipsis as truncate;

crates/op-editor-ui/src/widgets/design_md_panel/helpers.rs

@@ -9,13 +9,7 @@ pub(super) fn label_char_w(ch: char) -> f32 {
     }
 }
 
-pub(super) fn truncate(s: &str, max: usize) -> String {
-    if s.chars().count() <= max {
-        return s.to_string();
-    }
-    let kept: String = s.chars().take(max.saturating_sub(1)).collect();
-    format!("{kept}…")
-}
+pub(super) use crate::util::truncate_ellipsis as truncate;
 
 pub(super) fn hex_to_color(hex: &str) -> Color {
     match op_editor_core::parse_hex_rgb(hex) {

crates/op-editor-ui/src/widgets/git_panel.rs

@@ -919,10 +919,4 @@ impl<'a> GitPanel<'a> {
 }
 
 /// Char truncation with an ellipsis.
-pub(super) fn truncate(s: &str, max: usize) -> String {
-    if s.chars().count() <= max {
-        return s.to_string();
-    }
-    let kept: String = s.chars().take(max.saturating_sub(1)).collect();
-    format!("{kept}…")
-}
+pub(super) use crate::util::truncate_ellipsis as truncate;

crates/op-editor-ui/src/widgets/variables_panel/paint.rs

@@ -749,11 +749,4 @@ fn scalar_to_label(s: &VariableScalar) -> String {
     }
 }
 
-fn truncate(s: &str, max: usize) -> String {
-    if s.chars().count() <= max {
-        return s.to_string();
-    }
-    let mut out: String = s.chars().take(max - 1).collect();
-    out.push('…');
-    out
-}
+use crate::util::truncate_ellipsis as truncate;