viewer: click to copy values, amounts, and identifiers

Company details (EIN, state number, address, every profile value), an
entry's number and amount, an account's code and balance, a document's
file name and SHA-256 copy on click: a pointer and copy icon on hover,
a check for a moment after. Amounts copy as their exact plain decimal
(fmt::plain: no "$", commas, or parentheses; "-" for negatives); where a
click already drills down (report cells, register and transaction rows,
general ledger lines), a right-click menu copies the amounts, the entry
number, or the description. The sidebar's chain check copies the
journal head and data folder.

tests/copy.rs: every display style copies back to the exact value
(property), and clicking the EIN, an entry's amount, and its number puts
exactly that on the clipboard.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01GWVo7x3UHw5kwCUaWxiejX

crates/ledger-gui/src/pages/company.rs

@@ -20,7 +20,7 @@ fn kv(ui: &mut Ui, k: &str, v: &str) {
     // Narrow, the label goes above its value.
     if ui.available_width() < 360.0 {
         ui.label(RichText::new(k).font(theme::regular(12.0)).color(p.muted));
-        ui.add(egui::Label::new(RichText::new(v).font(theme::regular(13.0))).wrap());
+        widgets::copyable(ui, RichText::new(v).font(theme::regular(13.0)), v);
         ui.add_space(4.0);
         return;
     }
@@ -34,7 +34,7 @@ fn kv(ui: &mut Ui, k: &str, v: &str) {
             theme::regular(13.0),
             p.muted,
         );
-        ui.add(egui::Label::new(RichText::new(v).font(theme::regular(13.0))).wrap());
+        widgets::copyable(ui, RichText::new(v).font(theme::regular(13.0)), v);
     });
 }