feat(linkedin-studio): trend-store staleness nudge — SessionStart B-S3 [skip-docs]

SessionStart now warns (>=7d, warn-only) when the persistent trend store's
newest capture is stale, firing ONLY when the store already holds captures
(a never-scanned user is never nagged). Neutral wording — "scan for trends"
hits trend-spotter's own trigger; no hardcoded beat (de-niche invariant).

- store.ts: newestCaptureDate() — pure max-capturedAt staleness signal (SSOT)
- cli.ts: status [--json] subcommand (count + newest + daysStale)
- session-start.mjs: trendsNewestCapture() reads trends.json as raw JSON
  (no tsx spawn at session start) + the reminder line, beside import-staleness
- tests: +3 store tests (newestCaptureDate) + hook subprocess test (3 cases:
  >=7d fires, <7d silent, absent/empty silent + no crash)
- test-runner.sh: trends floor 21->24

Verified: trends 24/24 · all hook tests 131/131 · gate 89/0/0 · real render
confirms "Trend signals are N days old. Scan for trends…".

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01RigJBiRFNtFZKCz21qNbQ4

scripts/test-runner.sh

@@ -683,7 +683,7 @@ if [ -x "$TR_DIR/node_modules/.bin/tsx" ]; then
   TR_OUT=$( set +e; (cd "$TR_DIR" && npm test) 2>&1; echo "TR_EXIT:$?" )
   TR_EXIT=$(echo "$TR_OUT" | grep -oE 'TR_EXIT:[0-9]+' | grep -oE '[0-9]+' | head -1)
   TR_TESTS=$(echo "$TR_OUT" | grep -oE 'tests [0-9]+' | grep -oE '[0-9]+' | tail -1)
-  TRENDS_TESTS_FLOOR=21
+  TRENDS_TESTS_FLOOR=24  # B-S3: +3 newestCaptureDate tests (staleness signal)
   if [ "$TR_EXIT" = "0" ] && [ -n "$TR_TESTS" ] && [ "$TR_TESTS" -ge "$TRENDS_TESTS_FLOOR" ]; then
     pass "trends-store suite green: $TR_TESTS tests pass (floor $TRENDS_TESTS_FLOOR)"
   else

scripts/trends/src/cli.ts

@@ -6,6 +6,7 @@
  *                                       [--source <s>] [--summary "<s>"] [--store <path>]
  *   node --import tsx src/cli.ts query --topics <a,b>  [--store <path>] [--json]
  *   node --import tsx src/cli.ts list   [--since <YYYY-MM-DD>] [--limit <n>] [--store <path>] [--json]
+ *   node --import tsx src/cli.ts status [--store <path>] [--json]
  *
  * The capture agent (research-engine) calls `add` to fold a freshly-polled trend
  * into the store, and `query`/`list` to reason over accumulated history. The
@@ -19,6 +20,7 @@ import {
   defaultStorePath,
   history,
   loadStore,
+  newestCaptureDate,
   queryByTopic,
   saveStore,
 } from "./store.js";
@@ -55,7 +57,8 @@ function usage(msg: string): never {
     "usage:\n" +
       '  add --title "<t>" --url "<u>" --topics <a,b> [--source <s>] [--summary "<s>"] [--store <path>]\n' +
       "  query --topics <a,b> [--store <path>] [--json]\n" +
-      "  list [--since <YYYY-MM-DD>] [--limit <n>] [--store <path>] [--json]",
+      "  list [--since <YYYY-MM-DD>] [--limit <n>] [--store <path>] [--json]\n" +
+      "  status [--store <path>] [--json]",
   );
   process.exit(2);
 }
@@ -64,6 +67,11 @@ function today(): string {
   return new Date().toISOString().slice(0, 10);
 }
 
+/** Whole days from one ISO date to another (floor); negative if `from` is later. */
+function daysBetween(fromIso: string, toIso: string): number {
+  return Math.floor((new Date(toIso).getTime() - new Date(fromIso).getTime()) / 86400000);
+}
+
 function main(): void {
   const [command, ...rest] = process.argv.slice(2);
   const flags = parseFlags(rest);
@@ -140,6 +148,24 @@ function main(): void {
     return;
   }
 
+  if (command === "status") {
+    const store = loadStore(storePath);
+    const newest = newestCaptureDate(store);
+    const daysStale = newest === null ? null : daysBetween(newest, today());
+    if (asJson) {
+      console.log(JSON.stringify({ store: storePath, count: store.trends.length, newest, daysStale }));
+      return;
+    }
+    console.log(`Store: ${storePath}`);
+    console.log(`  trends: ${store.trends.length}`);
+    if (newest === null) {
+      console.log("  newest: — (empty store; no captures yet)");
+    } else {
+      console.log(`  newest: ${newest} (${daysStale}d ago)`);
+    }
+    return;
+  }
+
   usage(command ? `unknown command: ${command}` : "no command given");
 }
 

scripts/trends/src/store.ts

@@ -161,6 +161,17 @@ export function history(store: TrendStore, opts: HistoryOptions = {}): TrendReco
   return out;
 }
 
+/**
+ * The most recent capturedAt across the store (ISO date), or null when the
+ * store is empty. The staleness signal behind the SessionStart trend-freshness
+ * nudge (B-S3) and the `status` CLI subcommand: reuses history()'s newest-first
+ * ordering so the module has a single notion of "newest". Pure — the days-stale
+ * arithmetic (needs "today") lives in the caller, not here.
+ */
+export function newestCaptureDate(store: TrendStore): string | null {
+  return history(store, { limit: 1 })[0]?.capturedAt ?? null;
+}
+
 /**
  * Default store path under the per-user data dir (M0 data-path convention), so
  * the trend history survives plugin upgrades/reinstalls. `LINKEDIN_STUDIO_DATA`

scripts/trends/tests/store.test.ts

@@ -13,6 +13,7 @@ import {
   addTrend,
   queryByTopic,
   history,
+  newestCaptureDate,
 } from "../src/store.js";
 import { SCHEMA_VERSION } from "../src/types.js";
 import type { TrendStore } from "../src/types.js";
@@ -294,4 +295,39 @@ describe("trends store", () => {
       assert.deepEqual(h.map((t) => t.title), ["Newest"]);
     });
   });
+
+  describe("newestCaptureDate (B-S3 staleness signal)", () => {
+    test("empty store → null (no captures yet → no nudge)", () => {
+      assert.equal(newestCaptureDate(emptyStore()), null);
+    });
+
+    test("single trend → its capturedAt", () => {
+      const store = addTrend(emptyStore(), {
+        title: "Solo",
+        url: "https://example.com/solo",
+        source: "tavily",
+        capturedAt: "2026-06-05",
+        topics: ["x"],
+      }).store;
+      assert.equal(newestCaptureDate(store), "2026-06-05");
+    });
+
+    test("multiple trends → the max (newest) capturedAt, regardless of insertion order", () => {
+      let store = emptyStore();
+      for (const [title, capturedAt] of [
+        ["Middle", "2026-05-01"],
+        ["Newest", "2026-06-01"],
+        ["Oldest", "2026-04-01"],
+      ] as const) {
+        store = addTrend(store, {
+          title,
+          url: `https://example.com/${title}`,
+          source: "tavily",
+          capturedAt,
+          topics: ["x"],
+        }).store;
+      }
+      assert.equal(newestCaptureDate(store), "2026-06-01");
+    });
+  });
 });