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/js/main.js

@@ -44,6 +44,16 @@ window.onload = function() {
         cookie_set("client-id", uuid(), 10000);
     }
 
+    // Vue 1's async queue can drop dependent watcher updates when
+    // data props are mutated outside the normal event flow (e.g. from
+    // a `hashchange` listener that fires before Vue's tick scheduler
+    // has caught up). Disable async batching so every reactive write
+    // synchronously re-evaluates dependents — this matches Vue 1's
+    // older default and is what the legacy UI implicitly relied on.
+    if (Vue.config) {
+        Vue.config.async = false;
+    }
+
     // Register global components
     Vue.component("templated-input", require("./templated-input"));
     Vue.component("message", require("./message"));