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-cli/Cargo.toml

@@ -17,14 +17,20 @@ default = ["gui"]
 gui = ["dep:ledger-gui"]
 
 [dependencies]
+ledger-host = { path = "../ledger-host" }
 ledger-mcp = { path = "../ledger-mcp" }
 ledger-store = { path = "../ledger-store" }
 ledger-gui = { path = "../ledger-gui", optional = true }
 
 [dev-dependencies]
 chrono = "0.4"
+libc = "0.2"
+reqwest = "0.13"
+rmcp = { version = "3", features = ["client", "transport-streamable-http-client-reqwest"] }
+tokio = { version = "1", features = ["macros", "rt-multi-thread", "time"] }
 ledger-config = { path = "../ledger-config" }
 ledger-core = { path = "../ledger-core" }
+ledger-vault = { path = "../ledger-vault" }
 serde_json = "1"
 toml = "1"
 tempfile = "3"