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

hsmc-macros/tests/ui/t10_1_during_duplicate_field.rs

@@ -0,0 +1,28 @@
+//! t10.1: a single `during:` listing the same field twice is a compile error.
+use hsmc::statechart;
+
+#[derive(Debug, Clone)]
+pub enum Ev { Halt }
+
+pub struct Ctx {
+    pub a: u32,
+}
+
+statechart! {
+M {
+    context: Ctx;
+    events: Ev;
+    default(S);
+    terminate(Halt);
+
+    state S {
+        during: tick(a, a);
+    }
+}
+}
+
+async fn tick(_: &mut u32, _: &mut u32) -> Ev { Ev::Halt }
+
+impl MActions for MActionContext<'_> {}
+
+fn main() {}