feat(project): Establish initial IRTT workspace and protocol definitions

Set up the multi-crate project structure and add the core IRTT protocol with pinned dependencies for reproducible builds.

Cargo.toml

@@ -0,0 +1,13 @@
+[workspace]
+members = [
+    "crates/irtt-proto",
+    "crates/irtt-client",
+    "crates/irtt-stats",
+    "crates/irtt-cli",
+]
+resolver = "2"
+
+[workspace.package]
+edition = "2021"
+license = "Apache-2.0"
+rust-version = "1.75"