P2 slice 6: the viewer

`wanderbooks gui [BOOK]` finds the data root, reads settings from the
journal, the vault of the book, presence through ops/, Save a copy /
Open on every document, Save the W-9, the Export menu, and colour
schemes. One builder for the CPA package and the 1099 worksheet
(ledger-package), shared by the server and the viewer.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01T3gXMVt7XJPi6ens1or9Dj

crates/ledger-gui/tests/assets.rs

@@ -14,7 +14,7 @@ use ledger_gui::pages::assets::{MonthStatus, TaxFacts, missing_tax_notice, notic
 use ledger_gui::pages::journal::describe;
 use ledger_gui::{App, Source, attention, data, fmt, palette};
 use ledger_store::Store;
-use ledger_store::viewer::ViewerTarget;
+use ledger_store::ops::ViewerTarget;
 use proptest::prelude::*;
 use rust_decimal::Decimal;
 use std::path::{Path, PathBuf};
@@ -54,7 +54,6 @@ fn usd(cents: i64) -> Money {
 fn load(dir: &Path, today: NaiveDate) -> Books {
     data::load_once(&Source {
         data_dir: dir.join("books-data"),
-        books_toml: None,
         today: Some(today),
     })
     .unwrap()