Hunt the Wumpus, in two skins

A browser recreation of Gregory Yob's 1973 game. The rules are his and are
free to use; the sentences he wrote to explain them are not, and none of them
are here. Every line this game prints was written for it. NOTICE.md sets out
what is ours, what is not, and why -- the same argument the lemonade stand
makes about its own text, made before shipping rather than after.

Two skins over one game, and the period one is a Teletype rather than a
television. Wumpus is six years older than the Atari the lemonade stand runs
on. It lived on a timesharing service you telephoned and it printed on paper,
which is why the game asks you to remember things: there is no screen to look
back at. So 1973 is fanfold and black ink and a print head hammering out one
character at a time, and the remaster is the same cave with the lamp on. The
rules never differ, and neither does a single word.

The cave is proved rather than trusted. The adjacency table is typed out by
hand, because a generated dodecahedron comes out with an arbitrary numbering
and this is the numbering every listing has used since 1973 -- so a transcript
from a magazine still makes sense against it. Typed out means it can be typed
wrong, and a wrong table would not crash: it would quietly stop being a
dodecahedron while the game still played. cave.test.ts checks degree three,
symmetry, connectivity, a diameter of exactly five, and three pentagons
through every room.

The map is not allowed to know more than the paper. CaveMap draws only from
the rooms the hunter has stood in and the warnings those rooms gave, and it
marks suspects rather than answers. That guarantee is asserted in the engine
rather than in the component, because it is a property of the engine and would
still have to hold if the map were thrown away.

Drawing a solid flat took two attempts. Rooms 6 to 15 are not two pentagons at
different depths, they are one ten-room ring alternating inward and outward
wiring, and getting that wrong still draws and still looks cave-shaped. It is
much harder to read. The test checks the property that actually matters --
that no tunnel crosses another -- and was confirmed to fail against the bad
layout before it was believed.

The dial-in is a real Bell 103 call rather than a noise: dial tone at 350 and
440 Hz, Touch-Tone dialling, ringback at 440 and 480, the far modem's 2225 Hz
mark tone, then both ends keying at once through a telephone band. The screech
everybody remembers is a V.34 handshake from the 1990s and could not have
existed here.

38 tests. Typecheck clean.

public/favicon.svg

@@ -0,0 +1,9 @@
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 64 64">
+  <!-- The wumpus, at favicon size: all it can afford is a silhouette, two
+       eyes and the teeth. Drawn in code like everything else here. -->
+  <rect width="64" height="64" rx="12" fill="#2a2135"/>
+  <path d="M14 48 Q9 20 32 15 Q55 20 50 48 Z" fill="#9be36f" stroke="#16111f" stroke-width="3"/>
+  <circle cx="24" cy="30" r="4" fill="#16111f"/>
+  <circle cx="40" cy="30" r="4" fill="#16111f"/>
+  <path d="M20 40 L25 47 L30 40 L35 47 L40 40 L45 47" fill="none" stroke="#16111f" stroke-width="3" stroke-linejoin="round"/>
+</svg>