feat(cli): spacesh-cli scaffold — clap tree, one-shot client, command mapping

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

crates/spacesh-cli/Cargo.toml

@@ -0,0 +1,20 @@
+[package]
+name = "spacesh-cli"
+edition.workspace = true
+version.workspace = true
+
+[lib]
+name = "spacesh_cli"
+path = "src/lib.rs"
+
+[[bin]]
+name = "spacesh"
+path = "src/main.rs"
+
+[dependencies]
+spacesh-proto = { path = "../spacesh-proto" }
+clap.workspace = true
+clap_complete.workspace = true
+tokio = { workspace = true }
+serde_json.workspace = true
+anyhow.workspace = true