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/documents.rs

@@ -246,7 +246,11 @@ fn detail(ui: &mut Ui, b: &Books, a: &Attachment, shell: &mut Shell<'_>) {
                     }
                 });
             });
-            ui.label(RichText::new(&a.file_name).font(theme::bold(20.0)));
+            widgets::copyable(
+                ui,
+                RichText::new(&a.file_name).font(theme::bold(20.0)),
+                &a.file_name,
+            );
             ui.add_space(8.0);
             egui::Grid::new(("docfacts", a.id))
                 .num_columns(2)
@@ -265,8 +269,10 @@ fn detail(ui: &mut Ui, b: &Books, a: &Attachment, shell: &mut Shell<'_>) {
                     ui.label(fmt::timestamp(&a.created_at));
                     ui.end_row();
                     k(ui, "SHA-256");
-                    ui.add(
-                        egui::Label::new(RichText::new(&a.blob_sha).monospace().size(11.5)).wrap(),
+                    widgets::copyable(
+                        ui,
+                        RichText::new(&a.blob_sha).monospace().size(11.5),
+                        &a.blob_sha,
                     );
                     ui.end_row();
                     if let Some(e) = a.entry_id {