Add in-game field manual on the pause screen

A [?] HELP button (or H key) on the pause screen opens a seven-page
technical manual: controls, run loop, arsenal, mutations, implants,
bestiary and pressure/defense math. List pages render live from the
WEAPONS/ITEMS/PERKS/ENEMY_TYPES/BOSS_DEFS tables so values never drift.
Also unifies the sfxbank fetch cache-buster with the v36 bump.

js/state.js

@@ -32,6 +32,8 @@ const G = {
   recentHits: [],
   transition: 0,       // room transition fade
   muted: false,
+  pauseHelp: false,
+  helpPage: 0,
   sfxVol: 0.45,
   musicVol: 0.55,
   imagesLoaded: false,