P2 slice 4: access

Agent tokens (wb_ and 64 hex digits), one book and one name each, kept
only as SHA-256 in a chain log and in the OS keyring; made, listed and
revoked only through the admin socket (`wanderbooks token ...`). The
door checks them, scopes cover every tool, every call is in the access
log (fail closed), and the owner passphrase is an Argon2id hash.
Setup's terminal test waits for its prompts.

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

crates/ledger-host/src/lib.rs

@@ -7,7 +7,8 @@
 //! ends. Each part is a mode of the one `wanderbooks` executable:
 //! [`host::run`] (`wanderbooks host`), [`helper::run`] (`wanderbooks
 //! helper`), [`bridge::run`] (`wanderbooks mcp`), and the commands in
-//! [`commands`] (`serve`, `close`, `books`).
+//! [`commands`] (`serve`, `close`, `books`, `token`). Agents' tokens are
+//! kept in the OS keyring ([`tokens`]).
 
 #[cfg(unix)]
 pub mod bridge;
@@ -23,6 +24,7 @@ pub mod lease;
 pub mod opener;
 #[cfg(unix)]
 mod start;
+pub mod tokens;
 
 /// How a mode stops when it can't go on: the reason is already printed,
 /// and the number is the process's exit code.