feedback5 R5: split the field-view helpers out of the render app

PIXI loading, pick records, tunables, view kind, unit info and the asset / GL
host now live in public/js/render/app/*.js. createFieldView stays in app.js,
unchanged, and every name the file used to export is re-exported. One
pixiPromise. Two source pins follow the lines that moved.

public/js/render/app/pixi.js

@@ -0,0 +1,31 @@
+// public/js/render/app/pixi.js — load PIXI and pixi-spine once (one module-level promise).
+
+const VENDOR = { pixi: '/vendor/pixi.min.js', spine: '/vendor/pixi-spine.js' };
+
+let pixiPromise = null;
+
+function loadScript(src) {
+  return new Promise((resolve, reject) => {
+    const s = document.createElement('script');
+    s.src = src;
+    s.async = false;
+    s.onload = () => resolve();
+    s.onerror = () => reject(new Error(`failed to load ${src}`));
+    document.head.appendChild(s);
+  });
+}
+
+/** Make sure PIXI and PIXI.spine exist (classic scripts; loaded once). */
+export function ensurePixi() {
+  if (globalThis.PIXI && globalThis.PIXI.spine) return Promise.resolve(globalThis.PIXI);
+  if (!pixiPromise) {
+    pixiPromise = (async () => {
+      if (!globalThis.PIXI) await loadScript(VENDOR.pixi);
+      if (!globalThis.PIXI?.spine) await loadScript(VENDOR.spine);
+      if (!globalThis.PIXI || !globalThis.PIXI.spine) throw new Error('PIXI / pixi-spine unavailable');
+      return globalThis.PIXI;
+    })();
+    pixiPromise.catch(() => { pixiPromise = null; });
+  }
+  return pixiPromise;
+}