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/newer_journal.rs

@@ -50,7 +50,6 @@ fn books(tag: &str) -> DataDir {
 fn source(data: &Path) -> Source {
     Source {
         data_dir: data.to_path_buf(),
-        books_toml: None,
         today: NaiveDate::from_ymd_opt(2026, 10, 16),
     }
 }