macbook: add DWT daemon for bcm5974 touchpad

Hyprland's built-in disable-while-typing doesn't work on this
MacBook because the keyboard and touchpad share the same USB
device, breaking libinput's device pairing. Add a lightweight
Python daemon that watches keyboard events and inhibits the
touchpad via sysfs for 500ms after each keypress.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

hosts/FredOS-Macbook.nix

@@ -32,6 +32,66 @@
       HandleLidSwitchExternalPower = "suspend";
     };
 
+    # Disable-while-typing daemon for the bcm5974 touchpad.
+    # Hyprland's built-in DWT doesn't work because the keyboard and
+    # touchpad share the same USB device, breaking libinput's pairing.
+    systemd.services.macbook-dwt = {
+      description = "Disable touchpad while typing (bcm5974)";
+      after = [ "systemd-udevd.service" ];
+      wantedBy = [ "multi-user.target" ];
+      serviceConfig = {
+        Type = "simple";
+        Restart = "on-failure";
+        RestartSec = 3;
+        ExecStart = "${pkgs.python3.withPackages (p: [])}/bin/python3 ${pkgs.writeText "macbook-dwt.py" ''
+import glob, os, select, struct, time
+
+EVENT_SIZE = struct.calcsize("llHHi")
+EV_KEY = 0x01
+DWT_TIMEOUT = 0.5
+
+def find_event(name):
+    for p in sorted(glob.glob("/sys/class/input/event*/device/name")):
+        with open(p) as f:
+            if name in f.read():
+                return p.split("/")[4]
+    return None
+
+def main():
+    tp = find_event("bcm5974")
+    kb = find_event("Apple Internal Keyboard")
+    if not tp or not kb:
+        raise SystemExit(f"Devices not found: touchpad={tp}, keyboard={kb}")
+
+    inhibit = f"/sys/class/input/{tp}/device/inhibited"
+    active = False
+    last_key = 0.0
+
+    with open(f"/dev/input/{kb}", "rb") as f:
+        try:
+            while True:
+                timeout = max(0, DWT_TIMEOUT - (time.monotonic() - last_key)) if active else None
+                r, _, _ = select.select([f], [], [], timeout)
+                if r:
+                    data = os.read(f.fileno(), EVENT_SIZE * 64)
+                    for off in range(0, len(data) - EVENT_SIZE + 1, EVENT_SIZE):
+                        _, _, typ, _, val = struct.unpack("llHHi", data[off:off + EVENT_SIZE])
+                        if typ == EV_KEY and val:
+                            last_key = time.monotonic()
+                            if not active:
+                                open(inhibit, "w").write("1")
+                                active = True
+                if active and time.monotonic() - last_key >= DWT_TIMEOUT:
+                    open(inhibit, "w").write("0")
+                    active = False
+        finally:
+            open(inhibit, "w").write("0")
+
+main()
+''}";
+      };
+    };
+
     home-manager.users.fred = { pkgs, ... }: {
       wayland.windowManager.hyprland.settings.monitor = [{
         output   = "";