Dashboard options: windows.*, detent names, positive number types

- dashboard.windowMaxScale / windowDistance -> dashboard.windows.maxScale /
  distance
- windowCurvature: default -> initial, snapPixels/snapPoints ->
  detentPixels/detentPoints, dragThreshold -> dragThresholdPixels (also the
  patch's option keys; window-curvature VERSION 19); removed `snap` now
  points to detentPixels
- types.numbers.positive/nonnegative instead of number + range assertions
  (step <= max, initial/detentPoints <= max and distance min <= max stay)
- frame-controls patch accepts longPressMs from 300, like the option
  (VERSION 2)
- "SteamVR dashboard patch" in descriptions, which fit into 80 columns

Old names keep working with a rename warning.

modules/steam-close-button.nix

@@ -1,4 +1,4 @@
-# Close (X) button on the dashboard's Steam window. Dashboard patch
+# Close (X) button on the dashboard's Steam window. SteamVR dashboard patch
 # (steam-close-button/patch.js; "systemui" on 127.0.0.1:8087), registered only
 # when enabled; enables steamvr-debugger.nix (one SteamVR restart the first time).
 { config, lib, pkgs, ... }:
@@ -11,7 +11,7 @@ in {
   options.steamFrame.dashboard.steamCloseButton.enable = lib.mkEnableOption ''
     a Close (X) button on the dashboard's Steam window. It hides Steam
     (previous window or just the bar) until shown explicitly, e.g. via the
-    Steam tab. Dashboard patch; off removes it (next switch)'';
+    Steam tab. SteamVR dashboard patch; off removes it (next switch)'';
 
   config = lib.mkIf cfg.enable {
     steamFrame.uiPatches.patches = [ {