P2 slice 3: opening and closing the books (plan 3.9, D-21, D-23)

One wanderbooks executable. The books are open while the viewer, an
agent session or a terminal holds them: a host process takes leases on
a socket, starts the server (the hidden mode `wanderbooks server`) with
a pipe on its input, and closes it 10 s after the last lease ends. No
background service. One host even in a race (run/host.lock).

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

crates/ledger-mcp/src/tools/kept.rs

@@ -1166,7 +1166,9 @@ impl BooksServer {
     async fn export_settings(&self) -> Result<Json<ExportSettingsOut>, String> {
         let store = self.lock()?;
         let s = store.ledger().settings();
-        if !s.is_journaled() {
+        // Books in the data root read no file: theirs are the defaults
+        // until the first is set.
+        if !s.is_journaled() && !self.live().status().journaled {
             return Err(
                 "these books still read their settings file, which is the copy: move it in with books.import_settings first"
                     .into(),