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

Cargo.toml

@@ -11,3 +11,11 @@ repository = "https://git.swaits.com/swaits/wanderbooks"
 missing_docs = "warn"
 # `cargo kani` sets cfg(kani) for the proof harnesses.
 unexpected_cfgs = { level = "warn", check-cfg = ["cfg(kani)"] }
+
+# Argon2id at the plan's 64 MiB, three passes, takes seconds unoptimized:
+# its crates are built optimized in debug and test builds too.
+[profile.dev.package.argon2]
+opt-level = 3
+
+[profile.dev.package.blake2]
+opt-level = 3