feat: peer version exchange with soft-warn UI indicator

Adds a one-shot Hello message to the lan-mouse wire protocol so each
peer can display the other end's build commit hash and warn on
version mismatch. Soft-warn only — mismatched versions never refuse
traffic.

Wire change (lan-mouse-proto)
* `ProtoEvent::Hello { commit: [u8; 8] }` carries the 8-byte ASCII
  short commit from shadow_rs's `SHORT_COMMIT`. Encoded/decoded
  alongside the existing event variants.
* `EventType::Hello` is appended to the enum so existing IDs are
  untouched. Old peers receive the event, hit `InvalidEventId`, and
  silently skip it via the forward-compat handler in
  `connect.rs::receive_loop` — the connection is unaffected.

Daemon
* Connect side sends one Hello immediately after the DTLS handshake
  authenticates and before the ping_pong loop starts. Best-effort,
  fire-and-forget — `log::debug!` on send error.
* Listen side mirrors the peer's Hello with its own (same shape as
  the existing Ping → Pong reply), so the peer's connect-side
  receive_loop populates `ClientState::peer_commit` for that
  handle.
* The disconnect path clears `peer_commit` so a stale hash isn't
  shown after the connection drops.

IPC
* `ClientState::peer_commit: Option<[u8; 8]>`. `None` means the
  peer hasn't sent Hello yet — either fresh connection or older
  build that predates the event.

GTK
* `ClientObject` exposes `peer-commit` as an `Option<String>`
  property; `peer_commit_to_string` converts the wire `[u8; 8]` to
  the displayable hex.
* `lan_mouse_gtk::run` now takes the local commit and stashes it in
  a `OnceLock` so per-row UI can compare against each peer's hash.
* `ClientRow::refresh_version_status` re-renders the collapsed
  subtitle with Pango markup whenever the property changes:
   - matched → green   "peer version: <hex> · matched"
   - mismatch → orange "peer version: <hex> · ours: <hex>"
   - unknown → orange  "peer version: unknown · ours: <hex>"
* Window invokes `refresh_version_status` from
  `update_client_state` after writing the new property, and
  `bind` calls it once on row construction so the initial
  subtitle isn't blank.

Known limitation: state-change broadcasts from the network side
(set_alive / set_active_addr / set_peer_commit) don't currently
trigger a `FrontendEvent::State` directly; the UI picks up the
latest values on the next user-driven broadcast. Same pre-existing
behavior as the alive/active_addr fields.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

lan-mouse-gtk/src/client_object.rs

@@ -26,6 +26,7 @@ impl ClientObject {
                     .collect::<Vec<_>>(),
             )
             .property("resolving", state.resolving)
+            .property("peer-commit", peer_commit_to_string(state.peer_commit))
             .build()
     }
 
@@ -34,6 +35,14 @@ impl ClientObject {
     }
 }
 
+/// Render the 8-byte ASCII commit hash carried in
+/// [`lan_mouse_ipc::ClientState::peer_commit`] as a `String`. `None`
+/// in → `None` out (peer hasn't sent a Hello yet, or speaks an older
+/// proto).
+pub fn peer_commit_to_string(commit: Option<[u8; 8]>) -> Option<String> {
+    commit.and_then(|c| std::str::from_utf8(&c).ok().map(str::to_string))
+}
+
 #[derive(Default, Clone)]
 pub struct ClientData {
     pub handle: ClientHandle,
@@ -43,4 +52,5 @@ pub struct ClientData {
     pub position: String,
     pub resolving: bool,
     pub ips: Vec<String>,
+    pub peer_commit: Option<String>,
 }

lan-mouse-gtk/src/client_object/imp.rs

@@ -19,6 +19,7 @@ pub struct ClientObject {
     #[property(name = "position", get, set, type = String, member = position)]
     #[property(name = "resolving", get, set, type = bool, member = resolving)]
     #[property(name = "ips", get, set, type = Vec<String>, member = ips)]
+    #[property(name = "peer-commit", get, set, type = Option<String>, member = peer_commit)]
     pub data: RefCell<ClientData>,
 }
 

lan-mouse-gtk/src/client_row.rs

@@ -123,6 +123,12 @@ impl ClientRow {
         bindings.push(position_binding);
         bindings.push(resolve_binding);
         bindings.push(ip_binding);
+
+        // Render the initial collapsed subtitle from whatever
+        // peer_commit the ClientObject was created with. Subsequent
+        // changes are pushed by `Window::update_client_state` calling
+        // `refresh_version_status` after writing the new property.
+        self.refresh_version_status();
     }
 
     pub fn unbind(&self) {
@@ -150,4 +156,34 @@ impl ClientRow {
     pub fn set_dns_state(&self, resolved: bool) {
         self.imp().set_dns_state(resolved);
     }
+
+    /// Recompute the collapsed subtitle (Pango markup) based on the
+    /// current `peer-commit` property and the local build's commit.
+    /// Soft-warn semantics: a missing or mismatched peer commit
+    /// surfaces as orange text but never blocks traffic. Called by
+    /// the window after `update_client_state` writes the new
+    /// `peer-commit`. The dns-status icon is left to its existing
+    /// `set_dns_state` handler so the two indicators don't fight
+    /// for the same CSS class.
+    pub fn refresh_version_status(&self) {
+        let peer: Option<String> = self
+            .imp()
+            .client_object
+            .borrow()
+            .as_ref()
+            .and_then(|co| co.property::<Option<String>>("peer-commit"));
+        let local = crate::local_commit_str();
+        let markup = match peer.as_deref() {
+            None => format!(
+                r##"<span foreground="#ffaa33">peer version: unknown · ours: {local}</span>"##
+            ),
+            Some(p) if p == local.as_str() => format!(
+                r##"<span foreground="#33cc66">peer version: {p} · matched</span>"##
+            ),
+            Some(p) => format!(
+                r##"<span foreground="#ffaa33">peer version: {p} · ours: {local}</span>"##
+            ),
+        };
+        self.set_subtitle(&markup);
+    }
 }

lan-mouse-gtk/src/lib.rs

@@ -10,10 +10,27 @@ mod macos_privacy;
 mod macos_status_item;
 mod window;
 
-use std::{env, process, str};
+use std::{env, process, str, sync::OnceLock};
 
 use window::Window;
 
+/// Local build's commit hash, set once by [`run`] before the GTK
+/// main loop starts. Read by per-row UI to compare against each
+/// peer's [`lan_mouse_ipc::ClientState::peer_commit`] for the
+/// soft-warn version-mismatch indicator.
+pub(crate) static LOCAL_COMMIT: OnceLock<[u8; 8]> = OnceLock::new();
+
+/// Convenience: returns the local commit as an 8-char ASCII string,
+/// or a placeholder if unset (which would indicate a programmer
+/// error since [`run`] always sets it).
+pub(crate) fn local_commit_str() -> String {
+    LOCAL_COMMIT
+        .get()
+        .and_then(|c| std::str::from_utf8(c).ok())
+        .unwrap_or("????????")
+        .to_string()
+}
+
 use lan_mouse_ipc::FrontendEvent;
 
 use adw::Application;
@@ -31,8 +48,13 @@ pub enum GtkError {
     NonZeroExitCode(i32),
 }
 
-pub fn run() -> Result<(), GtkError> {
+pub fn run(local_commit: [u8; 8]) -> Result<(), GtkError> {
     log::debug!("running gtk frontend");
+    LOCAL_COMMIT
+        .set(local_commit)
+        .expect("local_commit set once");
+
+
     #[cfg(windows)]
     let ret = std::thread::Builder::new()
         .stack_size(8 * 1024 * 1024) // https://gitlab.gnome.org/GNOME/gtk/-/commit/52dbb3f372b2c3ea339e879689c1de535ba2c2c3 -> caused crash on windows

lan-mouse-gtk/src/window.rs

@@ -365,6 +365,13 @@ impl Window {
             .map(|ip| ip.to_string())
             .collect::<Vec<_>>();
         client_object.set_ips(ips);
+
+        /* peer build version (drives the version-match indicator) */
+        client_object.set_property(
+            "peer-commit",
+            crate::client_object::peer_commit_to_string(state.peer_commit),
+        );
+        row.refresh_version_status();
     }
 
     fn client_object_for_handle(&self, handle: ClientHandle) -> Option<ClientObject> {