initial commit: hsmc v0.2 with during: activities

Hierarchical statechart codegen for Rust with:
- during: activities for state-scoped concurrent I/O
- field-list borrowing (split-borrow inside the run loop)
- embassy-first async with tokio support
- STATE_CHART const for tooling/inspection
- examples: microwave, microwave_tui, embassy_full, during_radio

Cargo.toml

@@ -0,0 +1,8 @@
+[workspace]
+resolver = "2"
+members = ["hsmc", "hsmc-macros"]
+
+[workspace.package]
+version = "0.1.0"
+edition = "2021"
+license = "MIT OR Apache-2.0"