VR keyboard: cleanup of the controller bridge, gesture input and docs

- gesture-input.js: drop the unused mode getter and release().
- relay.mjs: both sides have a binding; no condition.
- hub.js: the frame cadence is documented once (bridge-patch.js); errors
  listed.
- docs: the bridge's idle cost and "one word at a time" stated once;
  twoHanded's README row points to the docs; rewrapped lines.

modules/vr-keyboard-controllers/hub.js

@@ -3,17 +3,16 @@
 // extraArgs (like lib/hooks.js): installs window.__sfuiControllers unless an
 // equal or newer VERSION is there (a newer one takes over the subscribers)
 // and evaluates to it. relay.mjs calls frame(f) with bridge-patch.js's
-// frames and lost() when the SteamVR side goes away.
+// frames (cadence there) and lost() when the SteamVR side goes away.
 //   subscribe(fn) -> unsubscribe   fn(frame) per frame, fn(null) when lost
 //   last                           the last frame (null: none / lost)
 //   demand(ms)                     full rate for the next ms (0: end), e.g.
 //                                  during a laser press; via the relay's
 //                                  CDP binding __sfuiCtlIn
+//   errors                         { count, last } of throwing subscribers
 // Each frame's hand points (tip, ray) get the keyboard page's px: x, y
 // (CSS px of the keyboard popup) and onKeyboard (inside the page), if the
-// keyboard popup exists. Frames come at up to ~90 Hz while a hand's tip is
-// within 10 cm of the keyboard or its trigger is pulled, else every 1 s, and
-// only while SteamVR shows the keyboard (then one with keyboard null).
+// keyboard popup exists.
 (() => {
   const VERSION = 2;
   const G = globalThis;

modules/vr-keyboard-controllers/relay.mjs

@@ -56,7 +56,7 @@ async function connect(side) {
   const closed = new Promise((res) => { ws.onclose = res; });
   // No Runtime.enable: bindings work without it, and it would stream the
   // page's console and context events here.
-  if (cfg.binding) send('Runtime.addBinding', { name: cfg.binding });
+  send('Runtime.addBinding', { name: cfg.binding });
   live[side] = (expression) => send('Runtime.evaluate', { expression });
   console.log(`${side}: connected`);
   await closed;