feat(cli): implement multi-applet binary dispatch and signal handling

crates/irtt-cli/src/applet.rs

@@ -0,0 +1,85 @@
+use std::path::Path;
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum RequestedApplet {
+    Client,
+    Tui,
+    Server,
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum AppletAvailability {
+    Client,
+    Tui,
+    Server,
+    None,
+}
+
+pub fn detect_applet_from_argv0(argv0: &str) -> Option<RequestedApplet> {
+    match Path::new(argv0)
+        .file_name()
+        .and_then(|name| name.to_str())
+        .unwrap_or(argv0)
+    {
+        "irtt-cli" => Some(RequestedApplet::Client),
+        "irtt-tui" => Some(RequestedApplet::Tui),
+        "irttd" | "irtt-server" => Some(RequestedApplet::Server),
+        "irtt-rs" => None,
+        _ => None,
+    }
+}
+
+pub const fn default_applet_for_features(
+    client_enabled: bool,
+    tui_enabled: bool,
+    server_enabled: bool,
+) -> AppletAvailability {
+    if client_enabled {
+        AppletAvailability::Client
+    } else if tui_enabled {
+        AppletAvailability::Tui
+    } else if server_enabled {
+        AppletAvailability::Server
+    } else {
+        AppletAvailability::None
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn applet_detection_maps_binary_names() {
+        assert_eq!(
+            detect_applet_from_argv0("/usr/bin/irtt-cli"),
+            Some(RequestedApplet::Client)
+        );
+        assert_eq!(
+            detect_applet_from_argv0("irtt-tui"),
+            Some(RequestedApplet::Tui)
+        );
+        assert_eq!(
+            detect_applet_from_argv0("irtt-server"),
+            Some(RequestedApplet::Server)
+        );
+        assert_eq!(detect_applet_from_argv0("irtt-rs"), None);
+        assert_eq!(detect_applet_from_argv0("custom-name"), None);
+    }
+
+    #[test]
+    fn default_applet_prefers_client_then_tui() {
+        assert_eq!(
+            default_applet_for_features(true, true, false),
+            AppletAvailability::Client
+        );
+        assert_eq!(
+            default_applet_for_features(false, true, false),
+            AppletAvailability::Tui
+        );
+        assert_eq!(
+            default_applet_for_features(false, false, false),
+            AppletAvailability::None
+        );
+    }
+}