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/observing.lua

@@ -0,0 +1,21 @@
+local narrator, describe, it, assert = ...
+
+local content = [[
+  VAR mood = "sadly"
+  ~ mood = "sunny"
+]]
+
+local book = narrator.parse_content(content)
+local story = narrator.init_story(book)
+
+local mood
+
+story:observe('mood', function(value)
+  mood = value
+end)
+
+story:begin()
+
+it('Sunny mood.', function()
+  assert.equal(mood, 'sunny')
+end)