[eric] browser: settle-aware in-batch wait and a terminal read sub-action

frontend/src/shared/browserSettle.ts

@@ -0,0 +1,30 @@
+// Renderer-side mirror of the backend's smart-wait (browser_wait.py): a `wait`
+// that returns the instant the page's network goes quiet instead of blind-sleeping
+// the full duration. A top-level BrowserWait already gets this on the backend, but
+// a `wait` INSIDE a BrowserBatch runs entirely here in the renderer, so without
+// this it would fall back to a dumb sleep and make batching slower than not batching.
+
+export const SETTLE_FLOOR_MS = 250; // never settle before this (a momentary gap isn't 'settled')
+export const SETTLE_QUIET_MS = 400; // network must be silent this long to count as settled
+export const SETTLE_POLL_MS = 150;
+
+// One probe: is the document complete, and how long since the last network resource
+// finished/started? Returns a JSON string. No interpolation, so it's injection-safe.
+export const SETTLE_PROBE_JS =
+  "(()=>{const n=performance.now();" +
+  "const es=performance.getEntriesByType('resource');let last=0;" +
+  "for(const e of es){const t=Math.max(e.responseEnd||0,e.startTime||0);if(t>last)last=t;}" +
+  "return JSON.stringify({ready:document.readyState==='complete',quiet:Math.round(n-last)});})()";
+
+// Pure decision: stop waiting once we're past the floor AND the document is complete
+// AND the network has been quiet for the settle window.
+export function shouldStopWaiting(
+  ready: boolean,
+  quietMs: number,
+  elapsedMs: number,
+  floorMs = SETTLE_FLOOR_MS,
+  quietWindowMs = SETTLE_QUIET_MS,
+): boolean {
+  if (elapsedMs < floorMs) return false;
+  return !!ready && (quietMs || 0) >= quietWindowMs;
+}