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/jumping.lua

@@ -0,0 +1,39 @@
+local narrator, describe, it, assert = ...
+
+local content = [[
+  A root line
+  === knot
+  A knot line
+  = stitch
+  A stitch line
+  === somewhere
+  - (label) A label line
+]]
+
+local book = narrator.parse_content(content)
+local story = narrator.init_story(book)
+
+story:begin()
+
+local paragraphs = story:continue()
+
+it('Jump to label.', function()
+  story:jump_to('somewhere.label')
+  local paragraphs = story:continue()
+  assert.equal(#paragraphs, 1)
+  assert.equal(paragraphs[1].text, 'A label line')
+end)
+
+it('Jump to stitch.', function()
+  story:jump_to('knot.stitch')
+  local paragraphs = story:continue()
+  assert.equal(#paragraphs, 1)
+  assert.equal(paragraphs[1].text, 'A stitch line')
+end)
+
+it('Jump to knot.', function()
+  story:jump_to('knot')
+  local paragraphs = story:continue()
+  assert.equal(#paragraphs, 1)
+  assert.equal(paragraphs[1].text, 'A knot line')
+end)