refactor(cache): keep the closed-block key helpers in a leaf module

Readers that tag a cell as a closed block no longer import the
invalidation module, which several tests replace wholesale. The cache
route test counts the slice's pre-fold cell apart from the route's two
cells, and the provenance test reads the shared pick's ORDER BY over its
grouped rows.

src/lib/cache/__tests__/closed-block-invalidation.test.ts

@@ -1,10 +1,7 @@
 import { beforeEach, describe, expect, it } from "vitest";
 
-import {
-  closedBlockKeyPart,
-  closedBlockUntouched,
-  invalidateUserMeasurements,
-} from "../invalidate";
+import { closedBlockKeyPart, closedBlockUntouched } from "../closed-block";
+import { invalidateUserMeasurements } from "../invalidate";
 import { caches, type ServerCache } from "../server-cache";
 
 const analytics = caches.analytics as ServerCache<{ v: number }>;

src/lib/cache/closed-block.ts

@@ -0,0 +1,23 @@
+/**
+ * The key part that marks an analytics entry as a closed block: a value that
+ * depends only on readings measured before `before`. Such a block is the
+ * same however many syncs land after it, as long as none of them touches a
+ * reading that old, so a measurement write that says how far back it
+ * reached (`touchedFrom`) leaves it in place. Every other invalidation, and
+ * every write that does not say, drops it as before.
+ */
+export function closedBlockKeyPart(before: Date | number): string {
+  const ms = typeof before === "number" ? before : before.getTime();
+  return `before:${ms}`;
+}
+
+const CLOSED_BLOCK_RE = /\|before:(\d+)(?:\||$)/;
+
+/**
+ * Whether `key` is a closed block that a write reaching back to
+ * `touchedFrom` cannot have changed. Exported for its test.
+ */
+export function closedBlockUntouched(key: string, touchedFrom: Date): boolean {
+  const match = CLOSED_BLOCK_RE.exec(key);
+  return match !== null && Number(match[1]) <= touchedFrom.getTime();
+}

src/lib/cache/invalidate.ts

@@ -20,6 +20,7 @@
 
 import { forgetCoverageProbe } from "@/lib/rollups/coverage-inflight";
 
+import { closedBlockUntouched } from "./closed-block";
 import { caches } from "./server-cache";
 
 /**
@@ -48,30 +49,6 @@ export function invalidateUserDashboardSnapshot(userId: string): void {
   caches.analytics.deleteByPrefix(dashboardSnapshotCacheKey(userId));
 }
 
-/**
- * The key part that marks an analytics entry as a closed block: a value that
- * depends only on readings measured before `before`. Such a block is the
- * same however many syncs land after it, as long as none of them touches a
- * reading that old, so a measurement write that says how far back it
- * reached (`touchedFrom`) leaves it in place. Every other invalidation, and
- * every write that does not say, drops it as before.
- */
-export function closedBlockKeyPart(before: Date | number): string {
-  const ms = typeof before === "number" ? before : before.getTime();
-  return `before:${ms}`;
-}
-
-const CLOSED_BLOCK_RE = /\|before:(\d+)(?:\||$)/;
-
-/**
- * Whether `key` is a closed block that a write reaching back to
- * `touchedFrom` cannot have changed. Exported for its test.
- */
-export function closedBlockUntouched(key: string, touchedFrom: Date): boolean {
-  const match = CLOSED_BLOCK_RE.exec(key);
-  return match !== null && Number(match[1]) <= touchedFrom.getTime();
-}
-
 /**
  * Invalidate every cache that may reflect a user's measurement set.
  *