feat: books.show — the agent puts things on the viewer's screen

books.show asks the viewer to open an entry, an account register, a
report (dates, month/quarter/year columns, prior-period or prior-year
comparison), a document, a search, or a page. The request lives outside
the books (runtime dir, keyed by data dir, written atomically); the
viewer watches it beside the journal and applies books before
navigating. 66 tools.

Site: the dashboard is the hero again; 'Here's what using it looks like'
shows the session beside the viewer, ending in books.show; the cash page
replaces the repeated overview lower down.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01MtYEaR6M6Ybdhm6X98BWNu

crates/ledger-gui/tests/live.rs

@@ -64,5 +64,27 @@ fn a_change_in_another_process_shows_up_live() {
     assert!(b.fresh.contains(&e), "the new entry is highlighted as new");
     assert!(b.seq() > first.seq());
     eprintln!("live update arrived in {:?}", started.elapsed());
+
+    // The agent asks the viewer to show the entry (books.show).
+    let asked = Instant::now();
+    ledger_store::viewer::request(
+        &data,
+        ledger_store::viewer::ViewerTarget::Entry { entry_id: e },
+    )
+    .unwrap();
+    let deadline = Instant::now() + Duration::from_secs(10);
+    let mut shown = false;
+    while Instant::now() < deadline {
+        if let Some(Update::Show(ledger_store::viewer::ViewerTarget::Entry { entry_id })) =
+            loader.wait(Duration::from_millis(200))
+        {
+            assert_eq!(entry_id, e);
+            shown = true;
+            break;
+        }
+    }
+    assert!(shown, "the show request never reached the viewer");
+    eprintln!("show request arrived in {:?}", asked.elapsed());
+    let _ = std::fs::remove_file(ledger_store::viewer::command_path(&data));
     let _ = std::fs::remove_dir_all(&dir);
 }

crates/ledger-gui/tests/show.rs

@@ -0,0 +1,73 @@
+//! books.show requests drive the viewer to the right place.
+
+use egui_kittest::Harness;
+use ledger_gui::nav::{ReportKind, Route};
+use ledger_gui::{App, Source, data};
+use ledger_store::viewer::ViewerTarget;
+
+#[test]
+fn show_requests_navigate_the_viewer() {
+    let today = chrono::NaiveDate::from_ymd_opt(2026, 10, 12).unwrap();
+    let dir = std::env::temp_dir().join(format!("ledger-gui-show-{}", std::process::id()));
+    let _ = std::fs::remove_dir_all(&dir);
+    ledger_gui::demo::build(&dir, today).unwrap();
+    let source = Source {
+        data_dir: dir.join("books-data"),
+        books_toml: Some(dir.join("wanderbooks.toml")),
+        today: Some(today),
+    };
+    let books = data::load_once(&source).unwrap();
+    let rent = books.ledger.chart().find_by_code("6200").unwrap().id;
+    let mut h = Harness::builder()
+        .with_size(egui::vec2(1440.0, 920.0))
+        .build_eframe(|cc| App::with_books(&cc.egui_ctx, books, true, Route::Overview));
+
+    // "Compare this quarter's P&L with the same quarter last year, by month."
+    h.state_mut().show(ViewerTarget::Report {
+        report: "profit_and_loss".into(),
+        start: Some("2026-07-01".into()),
+        end: Some("2026-09-30".into()),
+        columns: Some("month".into()),
+        compare: Some("prior_year".into()),
+    });
+    h.run_steps(2);
+    assert_eq!(
+        h.state_mut().route(),
+        &Route::Reports(ReportKind::ProfitAndLoss)
+    );
+    let st = &h.state_mut().state_mut().reports;
+    assert_eq!(
+        st.range,
+        ledger_gui::pages::reports::Range::Custom(
+            chrono::NaiveDate::from_ymd_opt(2026, 7, 1).unwrap(),
+            chrono::NaiveDate::from_ymd_opt(2026, 9, 30).unwrap()
+        )
+    );
+    assert_eq!(st.columns, ledger_gui::pages::reports::Columns::Month);
+
+    // "Show me the rent account for the summer."
+    h.state_mut().show(ViewerTarget::Account {
+        code: "6200".into(),
+        start: Some("2026-06-01".into()),
+        end: Some("2026-08-31".into()),
+    });
+    h.run_steps(2);
+    assert_eq!(h.state_mut().route(), &Route::Account(rent));
+
+    // "Find every Adobe charge."
+    h.state_mut().show(ViewerTarget::Search {
+        query: "adobe".into(),
+    });
+    h.run_steps(2);
+    assert_eq!(h.state_mut().route(), &Route::Transactions);
+    assert_eq!(h.state_mut().state_mut().transactions.query, "adobe");
+
+    // Unknown accounts are ignored, not crashes.
+    h.state_mut().show(ViewerTarget::Account {
+        code: "9999".into(),
+        start: None,
+        end: None,
+    });
+    assert_eq!(h.state_mut().route(), &Route::Transactions);
+    let _ = std::fs::remove_dir_all(&dir);
+}