feat: add Fn hotkey monitor and probe CLI

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

Sources/SstProbe/HotkeyProbe.swift

@@ -0,0 +1,16 @@
+import Foundation
+import CoreGraphics
+import SstCore
+
+func runHotkeyProbe() -> Never {
+    if !CGPreflightListenEventAccess() { _ = CGRequestListenEventAccess() }
+    let monitor = HotkeyMonitor()
+    monitor.onEvent = { print("hotkey:", $0) }
+    do { try monitor.start() } catch {
+        print("failed:", error.localizedDescription)
+        exit(1)
+    }
+    print("Houd Fn ingedrukt en laat los. Ctrl-C om te stoppen.")
+    RunLoop.main.run()
+    exit(0)
+}

Sources/SstProbe/main.swift

@@ -0,0 +1,9 @@
+import Foundation
+
+let command = CommandLine.arguments.dropFirst().first ?? "help"
+switch command {
+case "hotkey":
+    runHotkeyProbe()
+default:
+    print("usage: sst-probe hotkey")
+}