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

docs/mcp-interface.md

@@ -130,7 +130,9 @@ settings-and-conventions section says how to use them.
   evidence, parties, approval_rules }, settings_summary: [{ key, value,
   set_by, seq }], conventions: [{ id, kind, title, summary }], open_items:
   [{ id, title, due }], truncated, handbook_sections, next_steps: [{ tool,
-  args?, why }] }`. The connect text names it as the first call. Lists cut
+  args?, why }], isolation }`. The connect text names it as the first call.
+  `isolation` is `same_user (advisory)` (D-32): the books are hidden from
+  agents in the owner's own account, not locked against them. Lists cut
   to fit say so in `truncated` ("conventions: 4 more (books.conventions)").
   `focus` adds steps: `onboarding` the onboarding step, `close` the
   company's close steps, `audit` `books.verify`. Not built yet (P5):