chore: scaffold cargo workspace and crate skeletons

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

Cargo.toml

@@ -0,0 +1,27 @@
+[workspace]
+resolver = "2"
+members = [
+    "crates/spacesh-proto",
+    "crates/spacesh-pty",
+    "crates/spacesh-core",
+    "crates/spaceshd",
+]
+
+[workspace.package]
+edition = "2021"
+version = "0.1.0"
+
+[workspace.dependencies]
+tokio = { version = "1", features = ["full"] }
+tokio-util = { version = "0.7", features = ["codec"] }
+serde = { version = "1", features = ["derive"] }
+serde_json = "1"
+bytes = "1"
+base64 = "0.22"
+anyhow = "1"
+thiserror = "1"
+futures = "0.3"
+portable-pty = "0.8"
+alacritty_terminal = "0.25"
+fs2 = "0.4"
+dirs = "5"