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/narrator/test/runtime/set-get.lua

@@ -0,0 +1,30 @@
+local narrator, describe, it, assert = ...
+
+local content = [[
+  VAR x = 1
+  * [Change x to 1]
+  * [Change x to 2]
+  * [Change x to 3]
+  x = { x }
+]]
+
+local book = narrator.parse_content(content)
+local story = narrator.init_story(book)
+
+story:begin()
+
+it('The x is equal to 1.', function()
+  local x = story.variables['x']
+  assert.equal(x, 1)
+end)
+
+it('The x is changed to 3.', function()
+  local answer = 3
+  story.variables['x'] = answer
+  story:choose(answer)
+
+  local paragraphs = story:continue()
+  assert.equal(#paragraphs, 1)
+  assert.equal(paragraphs[1].text, 'x = 3')
+end)
+