fix: DSR replies to bare CSI n (missing default status-report parameter)

src/main/java/li/cil/oc2/common/vm/terminal/escapes/csi/DSR.java

@@ -7,6 +7,14 @@ public DSR(final Terminal terminal) {
         super(terminal);
     }
 
+    @Override
+    public int[] defaultParameters(CSIState state) {
+        // Ps omitted (or 0) defaults to 5 — device status report. CSIManager substitutes
+        // this before execute, so a bare CSI n replies \033[0n instead of hanging the guest
+        // waiting for a status response that never comes (§36 m4).
+        return new int[] {5};
+    }
+
     @Override
     public void execute(int[] args, int argCount, CSIState state) {
         if (args[0] == 5) {

src/test/java/li/cil/oc2/common/vm/terminal/TerminalBufferTest.java

@@ -130,6 +130,32 @@ void vpaMovesRowOnly() {
         assertEquals(6, terminal.y);
     }
 
+    @Test
+    void dsrBareCsiNRepliesStatus() {
+        // §36 m4: DSR (CSI Ps n) with no Ps defaults to Ps=5 (device status). CSIManager
+        // substitutes the handler's defaultParameters before execute, so a bare CSI n
+        // replies \033[0n instead of hanging a guest waiting for a status response.
+        write(terminal, CSI + "n");
+        final ByteBuffer reply = terminal.io.getInput();
+        assertNotNull(reply, "bare CSI n must produce a status-report reply");
+        final byte[] bytes = new byte[reply.remaining()];
+        reply.get(bytes);
+        assertEquals("\033[0n", new String(bytes, StandardCharsets.US_ASCII),
+                "bare CSI n replies operating-status (\\033[0n)");
+    }
+
+    @Test
+    void dsrExplicitFiveStillRepliesStatus() {
+        // Explicit Ps=5 is unchanged by the defaultParameters fix — still a status report.
+        write(terminal, CSI + "5n");
+        final ByteBuffer reply = terminal.io.getInput();
+        assertNotNull(reply, "CSI 5n must produce a status-report reply");
+        final byte[] bytes = new byte[reply.remaining()];
+        reply.get(bytes);
+        assertEquals("\033[0n", new String(bytes, StandardCharsets.US_ASCII),
+                "CSI 5n replies operating-status (\\033[0n)");
+    }
+
     @Test
     void cudMovesCursorDownAndClampsSaturatedCount() {
         // parseArgument saturates at Integer.MAX_VALUE; terminal.y + args[0] must not overflow to a