Frametop: a multi-screen desktop and universal 3D mouse for the Steam Frame

Several KDE Plasma screens floating in SteamVR, each a real monitor of any
resolution and shape, shown by our own compositor (ft-screens), with a
layout, wrist pinning, and visibility modes; a Bluetooth mouse that drives
all of SteamVR as a room-anchored 3D pointer (input relay, ft-pointer
helper, ft_pointer SteamVR driver); two settings apps; and Bluetooth LE
fixes. Installs on the headset with ./install.sh.

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

session/frametop.conf.example

@@ -0,0 +1,22 @@
+# Frametop settings, read by session/frametop-session.sh on the Frame.
+# Installed to ~/.config/frametop.conf. Environment variables with an FT_ prefix override these.
+BACKEND=screens    # screens: ft-screens, each screen its own resolution and size (set in Frametop Display Settings,
+                   #   saved in ~/.config/frametop-layout.json) | gamescope: the old path, settings below
+SCREENS=2          # gamescope: number of desktop screens (VR panels)
+WIDTH=1920         # gamescope: pixels per screen (at most 1920x1080 worth)
+HEIGHT=1080
+PHYS_WIDTH=1.6     # gamescope: panel width in metres, docked
+REMOTE=0           # 1 = serve the desktop over VNC on the tailnet (port 5900; see README)
+POINTER=0          # 1 = the mouse drives the universal 3D pointer (ft_pointer driver) instead of a plain mouse
+POINTER_SENSITIVITY=0.03   # degrees per mouse count
+POINTER_IDLE=30    # seconds without mouse use before the controllers get their laser back
+POINTER_WAKE_COUNTS=40     # mouse counts within 1 s needed to wake or re-claim the laser (ignores desk jitter)
+POINTER_DISTANCE=1.5       # metres to the cursor when it isn't on a panel
+POINTER_CURSOR_DEG=0.4     # size of the free-space dot, in degrees
+POINTER_ORIGIN_FRACTION=0.95 # laser starts this far along eye->cursor: its beam is a few cm, SteamVR's hit dot tiny
+POINTER_LASER_WIDTH=0.8    # controller beam width (dashboard.laserRayWidthScale), set once at helper start
+POINTER_ORIGIN_MARGIN=0.15   # the laser starts at least this far (m) in front of its target, so small floating controls stay hittable
+POINTER_SCENE_RADIUS=0.5   # texture-less dashboard overlays (dock, window controls): hit radius (m) around their origin
+POINTER_EDGE_REACH=0.3     # just off a panel, the cursor stays on its plane this far (m), to reach its resize edges and window controls
+LAYOUT_GRAB_OFFSET=0.075   # arranging screens: where the floating window's grab bar is, in metres below the screen
+LAYOUT_SLIDE_SPEED=0.5     # arranging screens: how fast the invisible controller slides a grabbed screen (m/s)