P2 slice 9: put the old copies aside after an adoption

`wanderbooks books put-aside ID DATA-DIR [--vault DIR --vault-key FILE]
[PATH...]` moves the old copies of adopted books (their data folder, their
TIN vault and its key, their settings file, the git history around them,
old exports) whole into numbered folders of their own in the root's
legacy/, a list of where each came from written and synced first. Nothing
is deleted. Refused unless the books hold everything the old copy does,
byte for byte (journal, stored files, vault records, key; what adoption
left behind and records the books sealed anew are listed and go aside
too); while a wanderbooks process holds it open for writing; when its
head moved since the preview; for links, paths named twice, inside the
root or missing, a vault or key given as a plain path, and paths on
another disk. Renames never replace anything, and a move cut short puts
back what it moved. Three review rounds of data safety.

The plan records the cutover's answers (Q-3: move the old copies aside;
the backup repository and folder).

Also: `connect`'s "the books fernhill' agent token" reads properly, and
the restart tests wait for a copied program to be runnable (a child forked
by another test while the copy was written made it "text file busy").

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

crates/ledger-cli/src/main.rs

@@ -16,7 +16,7 @@ fn print_usage() {
     eprintln!("usage: wanderbooks setup [--root PATH] [--home DIR]");
     eprintln!("       wanderbooks gui [BOOK | --root PATH --book ID | --data-dir PATH ...]");
     eprintln!(
-        "       wanderbooks books list | create ID | adopt DATA-DIR --id ID | restore BACKUP | back-up ID"
+        "       wanderbooks books list | create ID | adopt DATA-DIR --id ID | restore BACKUP | back-up ID | put-aside ID DATA-DIR [PATH...]"
     );
     eprintln!("       wanderbooks connect claude|codex --book ID");
     eprintln!(