test(e2e): un échec ne peut plus emporter les suivants, et les bornes sont mesurées

Trois choses, dont une qui explique pourquoi aucun diagnostic n'aboutissait.

SIGN_IN_MS valait 180 s alors que la somme de ses propres étapes en faisait 270.
La borne englobante se déclenchait donc TOUJOURS avant celle de l'étape en
cause, et ne pouvait dire qu'une chose : « bob-… to sign in ». Le message était
structurellement condamné à ne rien apprendre — on a cherché des jours une cause
que le harnais s'interdisait de nommer. Les bornes englobantes sont maintenant
des sommes calculées de leurs étapes.

Les parcours sont isolés. La suite déclare ses 7 parcours et leurs 27
vérifications AVANT tout lancement de navigateur, et rend donc toujours 34
lignes — y compris quand le montage meurt, où les parcours non exécutés sont
rapportés comme tels. Auparavant le total valait 24, 26 ou 27 selon ce qui
mourait : deux exécutions ne mesuraient même pas la même chose. Un échec est
contenu, pas absorbé — il reste compté.

Et chaque borne est dimensionnée sur une durée MESURÉE, inscrite à côté d'elle
dans le code. Le premier rendu d'un acteur prend 4,9 à 7,4 s et vaut 45 s ; la
traversée du broker 1,3 à 2,8 s et vaut 75 s. Un nombre nu n'apprend rien et
pourrit en silence.

Au passage : un walletPage.close() n'avait aucune borne du tout.

packages/polyfill/e2e/broker.ts

@@ -49,10 +49,21 @@ export const WALLET_PASSWORD = "ng-eventually-e2e";
 const BUILD_MS = 60_000;
 /** Launching a browser is local too — 30s is Playwright's own default, doubled. */
 const LAUNCH_MS = 60_000;
-/** Opening a page in a live browser is instant; a minute means the browser is not answering. */
-const NEW_PAGE_MS = 60_000;
-/** The whole wallet export measures ~7s against the real broker; two minutes is a hang. */
-const EXPORT_MS = 120_000;
+/**
+ * Opening a page in a live browser is instant — measured 0.0–0.1s over a batch. Bounded at
+ * 10s, which is a hundred times the measurement and still fails while a reader is watching.
+ * Exported because the applicative suite has to know it: a caller that wraps `newPage` in a
+ * TIGHTER bound of its own would fire first and report its own name instead of this one.
+ */
+export const NEW_PAGE_MS = 10_000;
+/**
+ * The whole wallet export measures ~7s against the real broker. Bounded at 60s ≈ 8x.
+ *
+ * Was two minutes, and that cost the batch of 2026-08-16 twice over: the export hung, and the
+ * suite spent two full minutes reaching a verdict it could have reached in one — before dying
+ * without a summary, because this runs in the SETUP, ahead of every journey.
+ */
+const EXPORT_MS = 60_000;
 
 const ENTRY = path.resolve(__dirname, "polyfill-entry.ts");
 const BUNDLE_OUT = path.resolve(__dirname, ".dist", "polyfill-entry.js");
@@ -538,9 +549,27 @@ export async function setupBrokerPage(page: Page, appUrl: string): Promise<Frame
 // dispatches on it, and stops when a frame is on the application's ORIGIN — an origin the
 // broker's pages can never be on, whatever they carry in their query string.
 
-/** One bound for the whole ceremony. Measured healthy: 2.6–3.9s; the newcomer's cold
- *  profile pays a broker session-start on top. Two minutes is a hang, not a slow host. */
-const BROKER_LOGIN_MS = 120_000;
+/**
+ * One bound for the whole ceremony — the screens, the clicks, and the application's frame
+ * attaching. Measured 1.3–2.8s for an actor and 1.7s on a cold profile's barrier passage
+ * (2026-08-16, `E2E_TIMINGS=1`). Bounded at 45s ≈ 16x the slowest measured: enough that a
+ * busy host does not manufacture a false diagnosis, little enough
+ * that the rich failure below — the screen, the trail, the frames, the page's own text —
+ * arrives in under a minute instead of after two.
+ *
+ * Exported for the same reason as {@link NEW_PAGE_MS}: this function's failure message is
+ * the most informative one in the harness, and an enclosing bound set below it would replace
+ * that message with "the round-trip timed out" and lose every fact in it.
+ */
+export const BROKER_LOGIN_MS = 45_000;
+/**
+ * What {@link setupBrokerPage} costs at worst: its navigation plus the ceremony. A caller
+ * that wants to MEASURE the round-trip should hand this to `measured` rather than invent a
+ * bound of its own — an enclosure below this number fires before the ceremony can explain
+ * itself, which is the failure mode `notebook.ts` documents at length.
+ */
+export const BROKER_ROUND_TRIP_MS = CONTEXT_NAVIGATION_MS + BROKER_LOGIN_MS;
+
 /** How often the browser re-reads the screen. Not a sleep: it is the interval of a
  *  condition check that runs INSIDE the page, the same mechanism `isVisible` uses. */
 const SCREEN_POLL_MS = 200;