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-cli/tests/one_executable.rs

@@ -108,7 +108,7 @@ fn each_mode_names_itself_in_its_usage() {
     let out = wanderbooks().arg("--help").output().unwrap();
     let err = String::from_utf8_lossy(&out.stderr);
     for line in [
-        "wanderbooks gui [DIR",
+        "wanderbooks gui [BOOK",
         "wanderbooks dev-stdio",
         "dev-stdio  run the books server",
     ] {
@@ -123,7 +123,7 @@ fn the_viewer_names_itself_in_its_usage() {
     assert!(out.status.success());
     let text = String::from_utf8_lossy(&out.stdout);
     assert!(
-        text.contains("usage: wanderbooks gui [--data-dir PATH]"),
+        text.contains("usage: wanderbooks gui [--root PATH] [--book ID]"),
         "{text}"
     );
 }