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/pick.js

@@ -0,0 +1,29 @@
+// public/js/render/app/pick.js — prep-piece facing and the pick record of a view.
+
+import { hitRectAt } from '../pick.js';
+
+const PIECE_DIRS = new Set(['UP', 'RIGHT', 'DOWN', 'LEFT']);
+
+/** Stored facing of a prep piece (m.private board pieces carry `dir`; bench pieces have none ⇒ undefined). */
+const pieceDirOf = (piece) => (typeof piece?.dir === 'string' && PIECE_DIRS.has(piece.dir.toUpperCase()) ? piece.dir.toUpperCase() : undefined);
+
+/**
+ * A view as a render/pick.js unit, or null when it cannot be picked (gone, faded out, dead): standing on the display
+ * tile it is drawn on, or — `walks` (battle enemies) — by its ground position and its drawn body (feet to head, on
+ * screen; a flying one by its body alone).
+ */
+function pickUnitOf(v, walks = false, hitArea = null) {
+  // a knocked-out operator lying on its tile waiting to redeploy (b.snap `down`, user playtest #4 item 9) is on that tile
+  // too: a press there selects it; other dead / dying views are gone
+  if (!v || v.destroyed || (v.alive === false && !v.down)) return null;
+  if (Number.isFinite(v.alpha) && v.alpha < 0.05) return null;
+  const sc = v.screen;
+  const body = walks && sc && sc.s > 0 && !v.culled ? { x: sc.x, top: Number.isFinite(sc.top) ? sc.top : sc.y, feet: sc.y, s: sc.s } : null;
+  const tile = walks ? null : { row: Math.round(v.y), col: Math.round(v.x) };
+  // a huge boss (data `hitArea`): its hit area on the ground and a body box as wide as it are pickable (render/pick.js)
+  const area = walks && !v.flying ? hitRectAt(v.x, v.y, hitArea) : null;
+  if (area && body) body.hw = hitArea.w / 2;
+  return { tile, x: v.x, y: v.y, fly: walks && !!v.flying, body, area, depth: v.root && !v.root.destroyed ? v.root.zIndex : 0, ref: v };
+}
+
+export { pieceDirOf, pickUnitOf };