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-scroll.test.ts

@@ -0,0 +1,81 @@
+import { describe, expect, it, vi } from "vitest";
+import {
+  clampPendingScrollClicks,
+  createScrollCoalescer,
+  isScrollButtonState,
+  MAX_SCROLL_CLICKS_PER_FLUSH,
+  SCROLL_FLUSH_INTERVAL_MS,
+  takeScrollClicks,
+} from "./guacamole-scroll.js";
+
+describe("guacamole scroll coalescing", () => {
+  it("caps a click flood so a laggy tunnel cannot queue a backlog", () => {
+    expect(clampPendingScrollClicks(0, 40)).toBe(MAX_SCROLL_CLICKS_PER_FLUSH);
+    expect(clampPendingScrollClicks(0, -40)).toBe(-MAX_SCROLL_CLICKS_PER_FLUSH);
+    expect(takeScrollClicks(20)).toEqual({
+      clicks: MAX_SCROLL_CLICKS_PER_FLUSH,
+      direction: 1,
+    });
+  });
+
+  it("sends the first notch immediately and drops later clicks in the same burst", () => {
+    const send = vi.fn();
+    let now = 1_000;
+    const scheduled: Array<{ fn: () => void; ms: number }> = [];
+    const coalescer = createScrollCoalescer(
+      send,
+      () => now,
+      (fn, ms) => {
+        scheduled.push({ fn, ms });
+        return scheduled.length;
+      },
+      () => {},
+    );
+
+    coalescer.notePointer({
+      x: 12,
+      y: 34,
+      left: false,
+      middle: false,
+      right: false,
+      up: false,
+      down: false,
+    });
+    for (let i = 0; i < 20; i++) coalescer.ingestClick(1);
+
+    const firstBurst = send.mock.calls.map(([state]) => state);
+    expect(firstBurst).toEqual([
+      {
+        x: 12,
+        y: 34,
+        left: false,
+        middle: false,
+        right: false,
+        up: false,
+        down: true,
+      },
+      {
+        x: 12,
+        y: 34,
+        left: false,
+        middle: false,
+        right: false,
+        up: false,
+        down: false,
+      },
+    ]);
+
+    send.mockClear();
+    now += SCROLL_FLUSH_INTERVAL_MS;
+    expect(scheduled).toHaveLength(1);
+    scheduled[0].fn();
+    expect(send.mock.calls).toHaveLength(MAX_SCROLL_CLICKS_PER_FLUSH * 2);
+    coalescer.dispose();
+  });
+
+  it("recognizes only the scroll buttons as coalesced input", () => {
+    expect(isScrollButtonState({ up: true, down: false })).toBe(true);
+    expect(isScrollButtonState({ up: false, down: true })).toBe(true);
+    expect(isScrollButtonState({ up: false, down: false })).toBe(false);
+  });
+});