Add toggleable numpad movement (Alt+Enter)

Ports the zMUD/CMUD numpad.set convention: plain numpad for normal
movement, Ctrl+numpad for moving up a level in that direction, and
Ctrl+Alt+numpad for moving down a level, all sent as literal MUD
commands via Accelerator. Alt+Enter toggles the whole set on/off (with
a sound + spoken confirmation) by clearing/restoring the accelerators,
so a disabled numpad types normally instead of doing nothing.

Cleared the numbers/*/-/+ entries in the world's native <keypad> block
since they'd otherwise double-send alongside the new Accelerator-based
bindings - left "." and "/" (hide/inventory) alone since those aren't
part of this feature. Documented the full three-layer key list and the
toggle in the readme.

cosmic rage/worlds/plugins/NumpadMovement.xml

@@ -0,0 +1,107 @@
+<?xml version="1.0" encoding="iso-8859-1"?>
+<!DOCTYPE muclient>
+
+<muclient>
+<plugin
+   name="NumpadMovement"
+   author="Antigravity"
+   id="3f8a1c6e7b2d49f0a5c8e6d1"
+   save_state="y"
+   language="Lua"
+   purpose="Toggleable numpad movement: plain numpad for normal movement, Ctrl for up-movement, Ctrl+Alt for down-movement."
+   requires="4.82"
+   version="1.0"
+   >
+</plugin>
+
+<!--  Script  -->
+<script>
+<![CDATA[
+-- Three layers of numpad bindings, matching the classic zMUD numpad.set
+-- convention: plain numpad for level movement, Ctrl+numpad for moving up
+-- a level while heading that direction, Ctrl+Alt+numpad for moving down
+-- a level while heading that direction. Alt+Enter toggles the whole set
+-- on/off, so the numpad can be freed up for typing numbers when needed.
+--
+-- Accelerator(key, "") clears a binding, and Accelerator(key, "command")
+-- with a plain string sends that command as if typed - this plugin just
+-- flips all of them on or off together rather than gating each key
+-- individually, so a disabled numpad behaves exactly like an unbound one
+-- (keys type normally) instead of silently swallowing keystrokes.
+
+local NUMPAD_BINDINGS = {
+  -- plain numpad - normal movement
+  { "Numpad1", "southwest" },
+  { "Numpad2", "south" },
+  { "Numpad3", "southeast" },
+  { "Numpad4", "west" },
+  { "Numpad5", "look" },
+  { "Numpad6", "east" },
+  { "Numpad7", "northwest" },
+  { "Numpad8", "north" },
+  { "Numpad9", "northeast" },
+  { "Numpad0", "exits" },
+  { "Multiply", "in" },
+  { "Ctrl+Multiply", "out" },
+  { "Subtract", "up" },
+  { "Add", "down" },
+
+  -- Ctrl+numpad - move up a level while heading that direction
+  { "Ctrl+Numpad1", "southwestup" },
+  { "Ctrl+Numpad2", "southup" },
+  { "Ctrl+Numpad3", "southeastup" },
+  { "Ctrl+Numpad4", "westup" },
+  { "Ctrl+Numpad6", "eastup" },
+  { "Ctrl+Numpad7", "northwestup" },
+  { "Ctrl+Numpad8", "northup" },
+  { "Ctrl+Numpad9", "northeastup" },
+  { "Ctrl+Subtract", "upstairs" },
+  { "Ctrl+Add", "downstairs" },
+
+  -- Ctrl+Alt+numpad - move down a level while heading that direction
+  { "Ctrl+Alt+Numpad1", "southwestdown" },
+  { "Ctrl+Alt+Numpad2", "southdown" },
+  { "Ctrl+Alt+Numpad3", "southeastdown" },
+  { "Ctrl+Alt+Numpad4", "westdown" },
+  { "Ctrl+Alt+Numpad5", "go" },
+  { "Ctrl+Alt+Numpad6", "eastdown" },
+  { "Ctrl+Alt+Numpad7", "northwestdown" },
+  { "Ctrl+Alt+Numpad8", "northdown" },
+  { "Ctrl+Alt+Numpad9", "northeastdown" },
+  { "Ctrl+Alt+Subtract", "climbup" },
+  { "Ctrl+Alt+Add", "climbdown" },
+}
+
+local function set_numpad_bindings(enabled)
+  for _, binding in ipairs(NUMPAD_BINDINGS) do
+    local key, command = binding[1], binding[2]
+    Accelerator(key, enabled and command or "")
+  end
+end
+
+function toggle_numpad()
+  local enabled = GetVariable("numpad_movement") ~= "0"
+  enabled = not enabled
+  SetVariable("numpad_movement", enabled and "1" or "0")
+  set_numpad_bindings(enabled)
+
+  if enabled then
+    ppi.play(dir.."sounds/ogg/general/misc/on.ogg", 0, 0, 100)
+    Execute("tts_interrupt Numpad movement enabled.")
+  else
+    ppi.play(dir.."sounds/ogg/general/misc/off.ogg", 0, 0, 100)
+    Execute("tts_interrupt Numpad movement disabled.")
+  end
+end
+
+function OnPluginInstall()
+  Accelerator("alt+enter", "toggle_numpad")
+  -- Enabled by default, matching the always-on native keypad behaviour
+  -- this plugin replaces.
+  local enabled = GetVariable("numpad_movement") ~= "0"
+  set_numpad_bindings(enabled)
+end
+]]>
+</script>
+
+</muclient>