P2 slice 8: the viewer's menu, setup, no confinement (D-32)

No Landlock, no seccomp, no helper: isolation is "same_user
(advisory)". The lease socket keeps two intents (close, format-upgrade
consent). The viewer holds the books open while it runs and gains a
Books menu: New books, Back up now, Restore (preview, then confirm),
Close, Connect Claude Code / Codex. New commands `wanderbooks books
back-up` and `wanderbooks connect claude|codex`. The scaffold
(`new`/`init` and its templates) is gone; install.sh needs no sudo.

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

crates/ledger-mcp/tests/spec_kept.rs

@@ -517,6 +517,8 @@ fn start_fits_in_8_kb() {
     let cut = start["truncated"].to_string();
     assert!(cut.contains("books.conventions"), "{cut}");
     assert!(start["conventions"].as_array().unwrap().len() >= 10);
+    // isolation_label_is_advisory (plan P2, D-32).
+    assert_eq!(start["isolation"], "same_user (advisory)");
 }
 
 /// Review of P1 (2026-10-17): the text imported is the file the server