ui: assorted polish - Vue async fix, OrbitControls passive listeners, path-viewer + motor-view + indicators

- main.js: disable Vue async batching so reactive writes from
  hashchange listeners propagate synchronously (matches Vue 1's older
  default; avoids dropped DRO updates).
- orbit.js: pass {passive:false} to wheel/touch listeners so
  OrbitControls.preventDefault() actually suppresses page panning.
- path-viewer: opaque dark canvas (no flash from page background),
  zero-size guard, ResizeObserver cleanup on destroy.
- motor-view: stop clobbering user edits with controller state.
- estop/indicators/tool-view/path-viewer pug: rename FA4 icons to FA6,
  add viewBox to estop SVG, fix tool-view trailing newline.

src/pug/templates/estop.pug

@@ -2,6 +2,8 @@ script#estop-template(type="text/x-template")
   svg(version="1.1", xmlns:svg="http://www.w3.org/2000/svg",
     xmlns="http://www.w3.org/2000/svg",
     xmlns:xlink="http://www.w3.org/1999/xlink",
+    viewBox="0 0 130 130",
+    preserveAspectRatio="xMidYMid meet",
     width="130", height="130")
       defs
         path#text-path-1(d="m 73.735,673.129 c 0,55.107 44.673,99.780 99.780,99.780 55.107,0 99.780,-44.673 99.780,-99.780 0,-55.107 -44.673,-99.780 -99.780,-99.780 -55.107,0 -99.780,44.673 -99.780,99.780 z")