feat: replace twelve thresholds with one sensitivity control that shows its limits (S8)

DECISIONS.md

@@ -1,6 +1,6 @@
 # Product decisions pending sign-off
 
-The implementation resolved four previously-undefined product questions. They
+The implementation resolved five previously-undefined product questions. They
 are reasonable defaults, but they should be confirmed (or changed) by product
 rather than remaining implicit in the code. Each notes where it lives so a
 change is a one-line edit.
@@ -38,9 +38,39 @@ flat history still tolerates normal PSI jitter.
 ## 4. Collection starts at the workspace's saved local time
 
 The first watched page initializes the workspace to **midnight in that user's
-browser timezone**. The Watchlist setting can override both time and IANA
+browser timezone**. The Settings screen can override both time and IANA
 timezone. Active pages receive stable offsets after the chosen start so the
 workspace does not burst every page or PSI sample simultaneously.
 
-- Where: `src/lib/collectionSchedule.ts`, the Watchlist settings panel, and the
+- Where: `src/lib/collectionSchedule.ts`, the Settings screen, and the
   collector's 15-minute due-page cron.
+
+## 5. Sensitivity is one control with three positions (option 10b)
+
+What a site considers worth reporting is **one setting**, not twelve. The three
+positions are Only big moves / Normal / Everything, and each resolves to a
+complete threshold set. The limits it resolves to are **displayed beneath the
+control, in the strings the digest itself writes**, so the abstraction is never
+opaque: a reader who wants to know why a line said "above the 250 ms you set"
+can see the 250 ms and see which position put it there.
+
+What the numbers are at each position is the part product should confirm. What
+is settled, and should not be reopened without a decision:
+
+- **Twelve per-metric thresholds** were rejected. Every number honest, and
+  nobody could say what any of them would do to tonight's digest.
+- **No thresholds at all** were rejected. The digest's threshold clause is the
+  reason a reader trusts the line, and it needs a setting behind it to be true.
+- **Per-page sensitivity** does not exist anywhere. S3 removed the page-detail
+  calibration panel and S8 gives it no new home; a site has one answer to "what
+  is worth telling you" because the digest that asks it is one message per site.
+- **No position resolves the savings gate to 0.** At 0 there is no limit the
+  reader set, so the digest withholds the clause and there is nothing to show
+  under the control. "Everything" is 1 ms, which is every measurement there is.
+- A site whose thresholds were hand-tuned before this landed is **mapped to the
+  nearest position and told once**, in the digest footer. Discarding somebody's
+  configuration silently is worse than the configuration was.
+
+- Where: `SENSITIVITY_THRESHOLDS` in `src/lib/sensitivity.ts` is the only place
+  the numbers appear; `DEFAULT_PERFORMANCE_THRESHOLDS` reads the Normal position
+  from it. The migration is `normalizeState` in `src/lib/store/normalize.ts`.

collector-worker/dataStore.ts

@@ -2,7 +2,7 @@ import { buildInitialState, buildSeedCruxEvidence, DEMO_DATA_VERSION } from "../
 import { captureAgentReadiness } from "../src/lib/agentScoring";
 import { resolveMarkerIndex } from "../src/lib/followups";
 import { mediansOf, pageTrend } from "../src/lib/scoring";
-import { effectivePerformanceThresholds } from "../src/lib/performanceThresholds";
+import { normalizePerformanceThresholds } from "../src/lib/performanceThresholds";
 import { normalizeState } from "../src/lib/store/normalize";
 import { TENANT, type AppState, type ChangeMarker, type Night } from "../src/lib/types";
 import {
@@ -217,7 +217,7 @@ export class FdeDataStore {
         desktop: mediansOf(night.scores.desktop),
       };
       page.agent = agent ?? [];
-      page.status = pageTrend(page, "mobile", effectivePerformanceThresholds(draft.performanceThresholds, page));
+      page.status = pageTrend(page, "mobile", normalizePerformanceThresholds(draft.performanceThresholds));
       page.runState = undefined;
       page.lastRunAt = night.iso ?? new Date().toISOString();
       page.lastCollectionStatus = "trusted";

src/app/(app)/pages/[id]/page.tsx

@@ -8,7 +8,7 @@ import { useIssuesView, useStore } from "@/components/store";
 import { CATEGORIES } from "@/lib/types";
 import type { CategoryKey, CollectionJob, Night, RangeDays, WatchPage } from "@/lib/types";
 import { agentReadinessHistoryPoints } from "@/lib/agentHistory";
-import { effectivePerformanceThresholds } from "@/lib/performanceThresholds";
+import { normalizePerformanceThresholds } from "@/lib/performanceThresholds";
 import {
   historyForStrategy,
   nightHasStrategy,
@@ -798,7 +798,7 @@ function ReadingsSection({
     ...run,
     startsDateGroup: run.dateKey !== runMetadata[index - 1]?.dateKey,
   }));
-  const thresholds = effectivePerformanceThresholds(store.performanceThresholds, page);
+  const thresholds = normalizePerformanceThresholds(store.performanceThresholds);
   const readinessHistory = agentReadinessHistoryPoints(
     agentRangeHistory,
     page.agentIgnores,
@@ -1301,7 +1301,7 @@ export default function PageDetail() {
   const collectionBlocked = page.flag === "paused" || (!!page.runState && page.runState !== "failed");
   const activeJob = store.jobs?.find((job) => job.runId === page.runId);
   const watchedPageHref = /^[a-z][a-z\d+.-]*:\/\//i.test(page.url) ? page.url : `https://${page.url}`;
-  const thresholds = effectivePerformanceThresholds(store.performanceThresholds, page);
+  const thresholds = normalizePerformanceThresholds(store.performanceThresholds);
   // A development-only comparison of the two trend renderings side by side.
   const isStatusPreview = process.env.NODE_ENV === "development" && searchParams.get("statusPreview") === "compare";
   const mobileTrend = isStatusPreview ? "regressing" : pageRangeTrend(page, "mobile", rangeDays, thresholds);

src/app/(app)/pages/pages-content.tsx

@@ -28,7 +28,7 @@ import type { SegmentRole } from "@/components/segmented-control";
 import { CATEGORIES } from "@/lib/types";
 import type { AgentIgnoreSettings, Night, WebflowRemediationLevel } from "@/lib/types";
 import { agentReadinessForNight, summarizeAgentChecks } from "@/lib/agentScoring";
-import { effectivePerformanceThresholds, normalizePerformanceThresholds } from "@/lib/performanceThresholds";
+import { normalizePerformanceThresholds } from "@/lib/performanceThresholds";
 import { historyForRange, pageAgentSnapshotForRange, pageRangeLatestNightForStrategy, pageRangeTrend } from "@/lib/scoring";
 import { flagChip, savingsValue } from "@/lib/ui";
 import { DESTINATION_LABEL, DESTINATION_PATH, QUEUE_LABEL } from "@/lib/vocabulary";
@@ -294,7 +294,7 @@ function DashboardContent({
   const nativeElementRollups = siteNativeElementRollups(activePages);
 
   const rows = pages.map((p, watchlistOrder) => {
-    const pageThresholds = effectivePerformanceThresholds(thresholds, p);
+    const pageThresholds = normalizePerformanceThresholds(thresholds);
     const mobileTrend = pageRangeTrend(p, "mobile", rangeDays, pageThresholds);
     const desktopTrend = pageRangeTrend(p, "desktop", rangeDays, pageThresholds);
     const visitorEvidence = evidenceForPage(visitorExperience, p.id, strategy);