feat: companion app improvements and intro overlay

Android: NES controller/keyboard enhancements, WebSocket reconnect,
portrait mode. Backend: remote input handler updates. UI: companion
intro overlay on dashboard, relay improvements.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

core/archipelago/src/api/handler/remote_input.rs

@@ -55,7 +55,13 @@ fn validate_key(key: &str) -> bool {
 #[serde(tag = "t")]
 enum InputCommand {
     #[serde(rename = "k")]
-    Key { k: String },
+    Key {
+        k: String,
+        /// Optional player ID (1 or 2) for multi-player arcade games.
+        /// When absent, input is broadcast without player tagging.
+        #[serde(default)]
+        p: Option<u8>,
+    },
     #[serde(rename = "m")]
     MouseMove { x: i32, y: i32 },
     #[serde(rename = "c")]
@@ -86,7 +92,7 @@ async fn handle_input(msg: &str) -> Result<Option<String>> {
         .context("invalid input command")?;
 
     match cmd {
-        InputCommand::Key { ref k } => {
+        InputCommand::Key { ref k, .. } => {
             if !validate_key(k) {
                 warn!("rejected key: {}", k);
                 return Ok(Some(r#"{"t":"e","m":"invalid key"}"#.to_string()));
@@ -124,6 +130,13 @@ impl ApiHandler {
         req: Request<hyper::Body>,
         relay_tx: broadcast::Sender<String>,
     ) -> Result<Response<hyper::Body>> {
+        // Extract optional player ID from query string: /ws/remote-input?p=1
+        let player_id: Option<u8> = req.uri().query()
+            .and_then(|q| q.split('&').find(|s| s.starts_with("p=")))
+            .and_then(|s| s.get(2..))
+            .and_then(|v| v.parse().ok())
+            .filter(|&p: &u8| p == 1 || p == 2);
+
         let (response, ws_fut_opt) = hyper_ws_listener::create_ws(req)
             .map_err(|e| anyhow::anyhow!("WebSocket upgrade failed: {}", e))?;
 
@@ -185,8 +198,28 @@ impl ApiHandler {
                                         continue; // silently drop
                                     }
 
-                                    // Always relay to browser clients (remote browser sessions)
-                                    let _ = relay_tx.send(text.clone());
+                                    // Relay to browser clients. If this connection has a
+                                    // player ID from query string and the message is a key
+                                    // event without a player field, inject it so the browser
+                                    // can route input to the correct player.
+                                    let relay_text = if let Some(pid) = player_id {
+                                        if text.contains(r#""t":"k""#) && !text.contains(r#""p":"#) {
+                                            // Insert "p":N before the closing brace
+                                            if let Some(pos) = text.rfind('}') {
+                                                let mut tagged = text[..pos].to_string();
+                                                tagged.push_str(&format!(r#","p":{}"#, pid));
+                                                tagged.push('}');
+                                                tagged
+                                            } else {
+                                                text.clone()
+                                            }
+                                        } else {
+                                            text.clone()
+                                        }
+                                    } else {
+                                        text.clone()
+                                    };
+                                    let _ = relay_tx.send(relay_text);
 
                                     match handle_input(&text).await {
                                         Ok(Some(reply)) => {