Vendor libs/hump, sfxrlua, json4lua, narrator as real files

These were committed as empty submodule gitlinks with no .gitmodules,
so the folders were never populated and the game could not load
(require of libs/hump/timer, libs/sfxrlua/sfxr, narrator.narrator).
Checked out each at its pinned commit and vendored the files, matching
the existing bundled-libs convention. Removed the junk libs/libs/ tree.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

libs/sfxrlua/README.md

@@ -0,0 +1,61 @@
+sfxr.lua
+========
+
+```
+luarocks install sfxr
+```
+
+A port of the sfxr sound effect synthesizer to pure Lua, designed to be used
+together with the *awesome* [LÖVE](https://love2d.org) game framework.
+
+Demo
+----
+
+To run the demo application you first need to download
+[LoveFrames](https://github.com/NikolaiResokav/LoveFrames) as a submodule:
+```
+git submodule update --init
+love demo
+```
+Note: Due to LoveFrames only supporting LÖVE 0.9.x, this dependency is inherited
+by the demo. A move to a new GUI framework is pending.
+
+Example usage
+-------------
+
+The following code examples demonstrate how to play a randomly generated sound:
+
+With [LÖVE](http://love2d.org):
+```lua
+local sfxr = require("sfxr")
+
+function love.load()
+    local sound = sfxr.newSound()
+    sound:randomize()
+    local sounddata = sound:generateSoundData()
+    local source = love.audio.newSource(sounddata)
+    source:play()
+end
+```
+
+With [lao](https://github.com/TheLinx/lao):
+```lua
+require("ao")
+local sfxr = require("sfxr")
+
+local driverId = ao.defaultDriverId()
+local device = ao.openLive(driverId, {bits = 16, rate = 44100, channels = 1})
+
+local sound = sfxr.newSound()
+sound:randomize()
+
+device:play(sound:generateString())
+```
+
+Documentation
+-------------
+
+[**The latest documentation build is available here**](http://nucular.github.io/sfxrlua/)
+
+This project uses [LDoc](http://stevedonovan.github.io/ldoc/) for autogenerated
+API documentation.