feat: move remote desktop (RDP/VNC/Telnet) into a first-party plugin

Relocates guacamole backend/frontend source and tests into
plugins/remote-desktop, following the ssh-terminal/docker pattern.

plugins/remote-desktop/frontend/guacamole-clipboard.ts

@@ -0,0 +1,39 @@
+import Guacamole from "guacamole-common-js";
+
+const CONTROL_LEFT_KEYSYM = 0xffe3;
+const V_KEYSYM = 0x76;
+
+interface ClipboardOutputStream {
+  sendBlob(data: string): void;
+  sendEnd(): void;
+}
+
+export interface GuacamoleClipboardClient {
+  createClipboardStream(mimetype: string): ClipboardOutputStream;
+  sendKeyEvent(pressed: number, keysym: number): void;
+}
+
+export function isPasteShortcut(
+  event: Pick<KeyboardEvent, "altKey" | "ctrlKey" | "key" | "metaKey">,
+): boolean {
+  return (
+    !event.altKey &&
+    (event.ctrlKey || event.metaKey) &&
+    event.key.toLowerCase() === "v"
+  );
+}
+
+export function pasteTextToRemote(
+  client: GuacamoleClipboardClient,
+  text: string,
+): void {
+  const stream = client.createClipboardStream("text/plain");
+  const writer = new Guacamole.StringWriter(stream);
+  writer.sendText(text);
+  writer.sendEnd();
+
+  client.sendKeyEvent(1, CONTROL_LEFT_KEYSYM);
+  client.sendKeyEvent(1, V_KEYSYM);
+  client.sendKeyEvent(0, V_KEYSYM);
+  client.sendKeyEvent(0, CONTROL_LEFT_KEYSYM);
+}