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-zoom.test.ts

@@ -0,0 +1,14 @@
+import { describe, expect, it } from "vitest";
+import { clampGuacamoleZoom, stepGuacamoleZoom } from "./guacamole-zoom.js";
+
+describe("guacamole zoom", () => {
+  it("steps in predictable quarter increments", () => {
+    expect(stepGuacamoleZoom(1, 1)).toBe(1.25);
+    expect(stepGuacamoleZoom(1, -1)).toBe(0.75);
+  });
+
+  it("keeps toolbar and pinch zoom within usable bounds", () => {
+    expect(clampGuacamoleZoom(0.1)).toBe(0.5);
+    expect(clampGuacamoleZoom(8)).toBe(4);
+  });
+});