Global hotkeys, in TeamSpeak's own shape

Bindings are captured system-wide rather than only while the window has
focus: X11's RECORD extension where the X server sees every key, and a
/dev/input reader as the Wayland fallback. Any key can act as a modifier,
mouse buttons included, as TS3 allows.

The action catalogue, its three categories and the "advanced actions"
split are reverse-engineered from the original client; actions this
client cannot perform are listed but greyed out. Push-to-talk becomes one
of these hotkeys, so the old focus-bound pushToTalkKey setting is gone and
the Voice Activation button edits that binding instead.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

ts3-client/swing/src/main/java/com/ts3client/ui/HotkeyService.java

@@ -0,0 +1,94 @@
+package com.ts3client.ui;
+
+import com.ts3client.hotkey.GlobalInputHook;
+import com.ts3client.hotkey.Hotkey;
+import com.ts3client.hotkey.HotkeyAction;
+import com.ts3client.hotkey.HotkeyCombo;
+import com.ts3client.hotkey.HotkeyEngine;
+import com.ts3client.hotkey.HotkeyKey;
+import com.ts3client.hotkey.Hotkeys;
+import com.ts3client.hotkey.desktop.DesktopInputHooks;
+
+import java.util.List;
+
+/**
+ * Owns the hotkey machinery for the UI: the stored bindings, the matching engine and
+ * the platform input hook they are fed from. Everything the dialogs need — recording a
+ * combination, naming keys, telling the user why hotkeys are dead — goes through here.
+ */
+final class HotkeyService {
+
+    private final Hotkeys hotkeys = Hotkeys.load();
+    private final HotkeyEngine engine;
+    private final GlobalInputHook hook;
+    private final HotkeyArguments arguments;
+
+    HotkeyService(HotkeyEngine.Handler handler, HotkeyArguments arguments) {
+        this.arguments = arguments;
+        engine = new HotkeyEngine(hotkeys, handler);
+        hook = DesktopInputHooks.start(engine);
+    }
+
+    /** The values this action's parameter can take right now, for the action tree. */
+    List<String> argumentChoices(HotkeyAction action) {
+        if (arguments == null || action.argument() == HotkeyAction.Argument.NONE) return List.of();
+        try {
+            return arguments.choices(action);
+        } catch (RuntimeException e) {
+            return List.of();
+        }
+    }
+
+    List<Hotkey> all() {
+        return hotkeys.all();
+    }
+
+    void replaceAll(List<Hotkey> updated) {
+        engine.releaseAll();
+        hotkeys.replaceAll(updated);
+        hotkeys.save();
+    }
+
+    /** The binding for an action with no argument, or {@code null} when unbound. */
+    Hotkey find(HotkeyAction action) {
+        synchronized (hotkeys.all()) {
+            for (Hotkey h : hotkeys.all()) {
+                if (h.action == action) return h;
+            }
+        }
+        return null;
+    }
+
+    boolean isRunning() {
+        return hook.isRunning();
+    }
+
+    /** One line for the options dialog: either working, or why it is not. */
+    String status() {
+        return hook.isRunning()
+                ? "Global hotkeys are active."
+                : "Global hotkeys are unavailable (" + hook.unavailableReason() + ").";
+    }
+
+    String display(HotkeyCombo combo) {
+        return combo == null ? "No hotkey assigned" : combo.display(this::keyName);
+    }
+
+    private String keyName(HotkeyKey key) {
+        return hook.keyName(key);
+    }
+
+    /** Captures the next combination instead of firing bindings; see {@link #stopRecording()}. */
+    void record(HotkeyEngine.Recorder recorder) {
+        engine.record(recorder);
+    }
+
+    void stopRecording() {
+        engine.stopRecording();
+    }
+
+    void dispose() {
+        engine.releaseAll();
+        hook.close();
+    }
+}