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/src/test_support.rs

@@ -118,7 +118,6 @@ impl Build {
         drop(self.s);
         let books = data::load_once(&Source {
             data_dir,
-            books_toml: None,
             today: Some(today()),
         })
         .unwrap();
@@ -270,7 +269,6 @@ pub(crate) fn old_books(name: &str) -> (TempDir, Books) {
     std::fs::copy(from.join("journal.jsonl"), data_dir.join("journal.jsonl")).unwrap();
     let books = data::load_once(&Source {
         data_dir,
-        books_toml: None,
         today: Some(today()),
     })
     .unwrap();