feedback1 integrate: form fx survive the render engine's stale-event drop; hidden-tab backlog compacted and flushed when a finished battle is shown; same-field re-entry buffered

- render/interp.js isCosmeticEvent: an fx with a form is state, never dropped as stale nor shed from a full queue;
  a late one switches the model without its telegraph, its closing clip shortened (render/app.js)
- battle/runner.js: a backlog past HELD_MAX keeps only the last status / skill toggle per unit; a battle that ended
  while the tab was hidden delivers its backlog and last snapshot when the tab is shown
- screens/game.js: a new field meta for the field on screen buffers its frames until the view re-enters it
- browser test stalls the main thread (blocking 1 s long tasks); Node tests drive the runner into the render buffer

test/render/forms.test.js

@@ -369,5 +369,10 @@ test('render/app.js renderInfo keeps UnitInfo `form` (it used to drop it: views
 
 test('render/app.js hands the `form` of a sim fx (shared/protocol.js fxForm) with the fx to the view and keeps the mode on the unit info', () => {
   const src = readFileSync(path.join(ROOT, 'public/js/render/app.js'), 'utf8');
-  assert.match(src, /const form = fxForm\(e\);[\s\S]{0,200}inf\.form = form[\s\S]{0,120}setForm\?\.\(form, e\[4\]\)/);
+  assert.match(src, /const form = fxForm\(e\);[\s\S]{0,250}inf\.form = form[\s\S]{0,250}setForm\?\.\(form, x\)/);
+  // a form fx handed out late (render/interp.js takeEvents `late`) switches the model with its closing clip shortened by
+  // the lateness and without replaying its telegraph
+  assert.match(src, /const x = late > 0 && Number\(e\[4\]\.dur\) > 0 \? \{ \.\.\.e\[4\], dur: Math\.max\(0, Number\(e\[4\]\.dur\) - late\) \} : e\[4\];/);
+  assert.match(src, /if \(!\(late > 0\)\) fx\.simFx\(/);
+  assert.match(src, /interp\.takeEvents\(renderT, EVS, renderT - 1\.5, LATE\);/);
 });