feat(properties): copy read-only property values to the clipboard

A read-only value cell is now click-to-copy: clicking writes the full,
un-elided value to the system clipboard (copy cursor on hover). One
change in render_ro_row, so it covers every read-only row for every
entity. Adds Message::PropCopyValue routed through iced:📋:write.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/app/mod.rs

@@ -1431,6 +1431,9 @@ pub enum Message {
     },
     /// User committed a geometry/common field edit (Enter pressed).
     PropGeomCommit(&'static str),
+    /// Copy a read-only property value to the system clipboard (click on a
+    /// read-only value cell). Carries the full, un-elided value.
+    PropCopyValue(String),
     /// User is typing in a block-attribute value field (live buffer update),
     /// keyed by the attribute tag.
     PropAttrInput { tag: String, value: String },

src/app/update/mod.rs

@@ -2107,6 +2107,8 @@ impl OpenCADStudio {
 
             Message::PropGeomCommit(field) => self.on_prop_geom_commit(field),
 
+            Message::PropCopyValue(value) => iced::clipboard::write(value),
+
             Message::PropAttrInput { tag, value } => {
                 self.tabs[self.active_tab]
                     .properties

src/ui/properties.rs

@@ -13,7 +13,9 @@ use std::fmt;
 use crate::ui::ROW_H;
 use acadrust::types::{Color as AcadColor, LineWeight};
 use acadrust::Handle;
-use iced::widget::{button, column, combo_box, container, row, scrollable, text, text_input};
+use iced::widget::{
+    button, column, combo_box, container, mouse_area, row, scrollable, text, text_input,
+};
 use iced::{Background, Border, Color, Element, Length, Padding, Theme};
 
 // ── Row-height-derived constants ─────────────────────────────────────────
@@ -865,7 +867,7 @@ fn render_bool_row<'a>(label: &'a str, field: &'static str, value: bool) -> Elem
 }
 
 fn render_ro_row<'a>(label: &'a str, value: &'a str) -> Element<'a, Message> {
-    let value = crate::ui::text_util::elide(value, 22);
+    let display = crate::ui::text_util::elide(value, 22);
     let label_col = container(text(crate::ui::text_util::elide(label, 18)).size(FONT_SZ).color(LABEL_COLOR))
         .style(|_: &Theme| container::Style {
             background: Some(Background::Color(LABEL_BG)),
@@ -880,7 +882,7 @@ fn render_ro_row<'a>(label: &'a str, value: &'a str) -> Element<'a, Message> {
             left: 6.0,
             right: 6.0,
         });
-    let value_col = container(text(value).size(FONT_SZ).color(VALUE_COLOR))
+    let value_inner = container(text(display).size(FONT_SZ).color(VALUE_COLOR))
         .style(|_: &Theme| container::Style {
             background: Some(Background::Color(VALUE_BG)),
             ..Default::default()
@@ -894,6 +896,16 @@ fn render_ro_row<'a>(label: &'a str, value: &'a str) -> Element<'a, Message> {
             left: 6.0,
             right: 6.0,
         });
+    // A read-only value is still copyable: click the value cell to copy the
+    // full (un-elided) text to the clipboard.
+    let value_col: Element<'a, Message> = if value.is_empty() {
+        value_inner.into()
+    } else {
+        mouse_area(value_inner)
+            .on_press(Message::PropCopyValue(value.to_string()))
+            .interaction(iced::mouse::Interaction::Copy)
+            .into()
+    };
     container(row![label_col, value_col])
         .height(Length::Fixed(ROW_H))
         .style(|_: &Theme| container::Style {