Add ft-floatd and the frametop-float KWin script

ft-floatd loads the script into the desktop's KWin, which reports windows
over D-Bus and takes commands through a long poll. Floating a window (the
window menu's Float in VR, Meta+Shift+F, or ft-float) turns on a spare
output sized to the window plus a margin, moves the window onto it, and
tells ft-screens the panel's crop, density, and place; docking puts it
back and turns the spare off. Tested on the headless test desktop; the
panel side in ft-screens comes next.

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

float/ft-float

@@ -0,0 +1,25 @@
+#!/usr/bin/env python3
+"""ft-float: talk to ft-floatd (floating windows in the Frametop desktop).
+
+  ft-float float [ID|active]   float a window (default: the active one; for it, a toggle)
+  ft-float dock [ID|active]    put a floating window back on the desktop
+  ft-float close ID            close a window
+  ft-float list                the spare outputs and what floats on them
+FT_FLOAT_SOCKET names ft-floatd's socket (default frametop_float).
+"""
+import os
+import socket
+import sys
+
+if len(sys.argv) < 2 or sys.argv[1] in ("-h", "--help"):
+    sys.exit(__doc__)
+s = socket.socket(socket.AF_UNIX, socket.SOCK_DGRAM)
+s.bind("")
+s.settimeout(5)
+try:
+    s.sendto(" ".join(sys.argv[1:]).encode(), "\0" + os.environ.get("FT_FLOAT_SOCKET", "frametop_float"))
+    reply = s.recv(8192).decode()
+except OSError as e:
+    sys.exit(f"ft-floatd didn't answer ({e}); is the Frametop desktop running?")
+print(reply)
+sys.exit(0 if reply.startswith("ok") else 1)