refactor(host/usb): bump hsmc to 0.5 and collapse WaitingForFirstFrame into Connected

hsmc 0.5 makes default(...) optional on every state. Drop the
WaitingForFirstFrame substate that existed only because 0.4 required
Connected to declare a default child — Connected itself is now the
resting "DTR up, no traffic yet" state, and on(FrameReceived) => Active
descends into the inactivity-timer state on the first byte. Behavior is
identical (entry/exit chain math unchanged); the chart has one fewer
state and one fewer default().

Display and Radio charts left as-is — their defaults are all classic
descents serving real grouping/lifecycle purposes (Splash grouping,
Bright sub-state isolation, RX/TX session lifecycle), not 0.4 artifacts.
No journal-replay tests in this repo, so the 0.5 journal-format change
does not apply.

Cargo.lock

@@ -1550,9 +1550,9 @@ checksum = "7f24254aa9a54b5c858eaee2f5bccdb46aaf0e486a595ed5fd8f86ba55232a70"
 
 [[package]]
 name = "hsmc"
-version = "0.4.1"
+version = "0.5.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "adbdeff427849daf4d03395027c8538dcdd02a0a26c6e59745f8647f5e657527"
+checksum = "a3951a3170ce7aa0f0bf4627ac4cc650857f15449c98e97647fa29fcd19c6d33"
 dependencies = [
  "defmt 0.3.100",
  "embassy-futures",
@@ -1564,9 +1564,9 @@ dependencies = [
 
 [[package]]
 name = "hsmc-macros"
-version = "0.4.1"
+version = "0.5.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "66ae4d525e3047234d69597f616c89b9ad49ac6a851e4522322a9d74fc2cc1bf"
+checksum = "4b6d97dd1d31fba9e2f96c65c0ce38d7bc1ff59abe775a0ae18e14dfae01d1d1"
 dependencies = [
  "proc-macro2",
  "quote",

Cargo.toml

@@ -33,7 +33,7 @@ embassy-usb-driver = "0.2"
 ucobs = { version = "0.3", features = ["legacy-msrv"] }
 heapless = "0.9"
 donglora-protocol = "1"
-hsmc = { version = "0.4", default-features = false, features = ["embassy", "trace-defmt"] }
+hsmc = { version = "0.5", default-features = false, features = ["embassy", "trace-defmt"] }
 # Local path while iterating on CAD IRQ-clear / standby-after-CAD fixes.
 # Switch back to git fork (then crates.io) once changes are upstreamed.
 lora-phy = { path = "../../lora-rs/lora-phy", features = ["defmt-03"] }

src/host/usb.rs

@@ -3,11 +3,11 @@
 //! ```text
 //! Host
 //! ├── Disconnected   (default)   no DTR
-//! └── Connected                            host attached
+//! └── Connected                  host attached, DTR up
-//!     ├── WaitingForFirstFrame (default)   DTR up, no traffic yet
+//!     │                          resting here means no traffic yet —
-//!     │                                    NO inactivity timer (boot quiet
+//!     │                          NO inactivity timer (boot quiet is
-//!     │                                    is normal — chart structurally
+//!     │                          normal; chart structurally blocks the
-//!     │                                    blocks the spurious 1s fire).
+//!     │                          spurious 1s fire).
 //!     └── Active                 ≥1 frame seen since connect
 //!                                inactivity timer (1s) armed and
 //!                                restarted by every frame via
@@ -18,8 +18,8 @@
 //! 1. **No spurious inactivity at boot.** The 1-second timer only exists
 //!    in `Active`, which requires a `FrameReceived` event to enter.
 //!    A freshly-connected host that holds DTR high but sends nothing
-//!    sits in `WaitingForFirstFrame` indefinitely — no timer, no warn,
+//!    rests at `Connected` indefinitely (hsmc 0.5 optional-default
-//!    no Reset cascade.
+//!    "microwave Standby" pattern) — no timer, no warn, no Reset cascade.
 //! 2. **Chart-owned timer scope.** Per hsmc README rule §7 (timers
 //!    armed by state lifecycle), the inactivity timer is cancelled on
 //!    every exit of `Active`, restarted on every entry. No global
@@ -58,8 +58,8 @@ const POLL_INTERVAL_MS: u64 = 100;
 pub enum HostInput {
     DtrRaised,
     DtrDropped,
-    /// A USB read returned ≥1 byte. Drives `WaitingForFirstFrame →
+    /// A USB read returned ≥1 byte. Drives `Connected → Active` on
-    /// Active` (first frame after connect) and the `Active → Active`
+    /// the first frame after DTR up, and the `Active → Active`
     /// self-transition that restarts the inactivity timer per
     /// hsmc README rule §4 (self-transition exits + re-enters target,
     /// re-arming its timer).
@@ -122,24 +122,21 @@ statechart! {
             entry: wake_display;
             exit: reset_radio, reset_display;
             on(DtrDropped) => Disconnected;
-            default(WaitingForFirstFrame);
+            // hsmc 0.5 microwave-Standby pattern: Connected itself is the
-
+            // resting "DTR up, no traffic yet" state. No inactivity timer
-            // Default child of Connected. No inactivity timer yet —
+            // here — boot quiet is normal (mux-rs holds DTR high before
-            // a freshly-connected host that hasn't sent its first byte
+            // any client attaches), so the chart structurally cannot fire
-            // is normal (mux-rs holds DTR high before any client
+            // a 1 s warn before the first byte. The first FrameReceived
-            // attaches). Stays here indefinitely until the first
+            // descends into Active, which owns the inactivity timer.
-            // frame arrives.
-            state WaitingForFirstFrame {
             on(FrameReceived) => Active;
-            }
 
             // Inactivity timer is chart-scoped: armed on every entry to
-            // Active (whether from WaitingForFirstFrame or self-loop
+            // Active (from Connected on the first frame, or from the
-            // after a frame), cancelled on every exit (per hsmc README
+            // self-transition below on each subsequent frame), cancelled
-            // rule §7). The self-transition `on(FrameReceived) =>
+            // on every exit (per hsmc README rule §7). The self-transition
-            // Active` re-enters Active per rule §4, re-arming the
+            // re-enters Active per rule §4, re-arming the timer —
-            // timer — equivalent to the "reset last_frame_at on each
+            // equivalent to the "reset last_frame_at on each byte" pattern
-            // byte" pattern but expressed in chart shape.
+            // but expressed in chart shape.
             //
             // hsmc's `after` triggers want `hsmc::Duration` (re-export
             // of `core::time::Duration`), not `embassy_time::Duration`.
@@ -275,9 +272,9 @@ async fn protocol_loop<'d, D: embassy_usb_driver::Driver<'d>>(
                     n,
                     receiver.dtr(),
                 );
-                // Drives WaitingForFirstFrame → Active on first byte
+                // Drives Connected → Active on first byte and
-                // and Active → Active (timer-restart) on every byte
+                // Active → Active (timer-restart) on every byte after.
-                // after. The chart owns inactivity from here.
+                // The chart owns inactivity from here.
                 let _ = machine.dispatch(HostInput::FrameReceived).await;
                 dispatch_bytes(&mut decoder, &read_buf[..n], commands, outbound).await;
             }
@@ -385,9 +382,9 @@ async fn protocol_loop<'d, D: embassy_usb_driver::Driver<'d>>(
 
         // DTR edge detection — drives Connected / Disconnected
         // transitions. The chart's `current_state()` may be
-        // Disconnected, Connected/WaitingForFirstFrame, or
+        // Disconnected, Connected (resting), or Connected/Active.
-        // Connected/Active per the new hierarchy. We're connected if
+        // We're connected if current state is anywhere inside
-        // current state is anywhere inside Connected.
+        // Connected.
         let dtr_high = receiver.dtr();
         let was_connected = !matches!(
             machine.current_state(),