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/units/branching.ink

@@ -0,0 +1,21 @@
+-> back_in_london
+
+=== back_in_london ===
+
+We arrived into London at 9.45pm exactly.
+*   'There is not a moment to lose!'[] I declared.
+    -> hurry_outside
+*   'Monsieur, let us savour this moment!'[] I declared.
+    My master clouted me firmly around the head and dragged me out of the door.
+    -> dragged_outside
+*   [We hurried home] -> hurry_outside
+
+=== hurry_outside ===
+We hurried home to Savile Row -> as_fast_as_we_could
+
+=== dragged_outside ===
+He insisted that we hurried home to Savile Row
+-> as_fast_as_we_could
+
+=== as_fast_as_we_could ===
+<> as fast as we could.