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

hooks/scripts/__tests__/session-start-trends-staleness.test.mjs

@@ -0,0 +1,79 @@
+import { describe, test } from 'node:test';
+import assert from 'node:assert/strict';
+import { execFileSync } from 'node:child_process';
+import { mkdtempSync, rmSync, mkdirSync, writeFileSync, copyFileSync } from 'node:fs';
+import { join, dirname } from 'node:path';
+import { tmpdir } from 'node:os';
+import { fileURLToPath } from 'node:url';
+
+// B-S3: SessionStart emits a warn-only "trend signals are N days old" nudge,
+// driven by the trend store's newest capturedAt, and ONLY when the store already
+// holds captures. session-start is a procedural hook with no exports, so we run
+// it as a subprocess with an isolated HOME + LINKEDIN_STUDIO_DATA and inspect the
+// additionalContext. Pattern: session-start-remember.test.mjs subprocess harness.
+const here = dirname(fileURLToPath(import.meta.url));
+const hookPath = join(here, '..', 'session-start.mjs');
+const PLUGIN_ROOT = join(here, '..', '..', '..');
+const STATE_TEMPLATE = join(PLUGIN_ROOT, 'config', 'state-file.template.md');
+
+const NUDGE = 'Trend signals are';
+const isoDaysAgo = (n) => new Date(Date.now() - n * 86400000).toISOString().slice(0, 10);
+
+// Run the hook against an isolated HOME + data root; optionally seed a trend
+// store. Returns the additionalContext string the hook injected at session start.
+function runHook({ captures }) {
+  const home = mkdtempSync(join(tmpdir(), 'lis-ts-home-'));
+  const data = mkdtempSync(join(tmpdir(), 'lis-ts-data-'));
+  try {
+    // The reminders block only runs when the state file already exists; the
+    // template is the canonical valid state, so copy it into the isolated HOME.
+    mkdirSync(join(home, '.claude'), { recursive: true });
+    copyFileSync(STATE_TEMPLATE, join(home, '.claude', 'linkedin-studio.local.md'));
+
+    if (captures) {
+      mkdirSync(join(data, 'trends'), { recursive: true });
+      writeFileSync(
+        join(data, 'trends', 'trends.json'),
+        JSON.stringify({ schemaVersion: 1, trends: captures }),
+      );
+    }
+
+    const stdout = execFileSync('node', [hookPath], {
+      input: '',
+      env: { ...process.env, HOME: home, USERPROFILE: home, LINKEDIN_STUDIO_DATA: data },
+      encoding: 'utf-8',
+    });
+    return JSON.parse(stdout).hookSpecificOutput.additionalContext;
+  } finally {
+    rmSync(home, { recursive: true, force: true });
+    rmSync(data, { recursive: true, force: true });
+  }
+}
+
+const trend = (capturedAt) => ({
+  id: 't' + capturedAt,
+  title: 'Some trend ' + capturedAt,
+  url: 'https://example.com/' + capturedAt,
+  source: 'tavily',
+  capturedAt,
+  topics: ['x'],
+});
+
+describe('session-start — trend-store staleness nudge (B-S3)', () => {
+  test('fires when newest capture is >=7 days old', () => {
+    const ctx = runHook({ captures: [trend('2026-01-01'), trend(isoDaysAgo(10))] });
+    assert.ok(ctx.includes(NUDGE), 'expected the trend-staleness nudge for a 10-day-old store');
+  });
+
+  test('does NOT fire when newest capture is fresh (<7 days)', () => {
+    const ctx = runHook({ captures: [trend(isoDaysAgo(2))] });
+    assert.ok(!ctx.includes(NUDGE), 'a 2-day-old store must not trigger the nudge');
+  });
+
+  test('does NOT fire (and does not crash) when the store is absent/empty', () => {
+    const absent = runHook({ captures: null });
+    assert.ok(!absent.includes(NUDGE), 'no store => no nudge');
+    const empty = runHook({ captures: [] });
+    assert.ok(!empty.includes(NUDGE), 'empty store => no nudge (never-scanned user is never nagged)');
+  });
+});

hooks/scripts/session-start.mjs

@@ -29,6 +29,28 @@ function daysSince(dateStr) {
   return Math.floor((Date.now() - epoch) / 86400000);
 }
 
+// B-S3: newest trend capture (ISO date) from the persistent trend store, read
+// as raw JSON. The hook must NOT spawn the tsx CLI at session start (slow +
+// needs node_modules/tsx); the store schema (trends[].capturedAt) is stable and
+// versioned, so a direct read is safe. Twin of scripts/trends/src/store.ts:
+// newestCaptureDate (max capturedAt). Returns null when the store is absent,
+// unreadable, or empty — no captures yet ⇒ no nudge.
+function trendsNewestCapture(storePath) {
+  if (!existsSync(storePath)) return null;
+  try {
+    const parsed = JSON.parse(readFileSync(storePath, 'utf-8'));
+    const trends = Array.isArray(parsed?.trends) ? parsed.trends : [];
+    let newest = null;
+    for (const t of trends) {
+      const d = typeof t?.capturedAt === 'string' ? t.capturedAt : null;
+      if (d && (newest === null || d > newest)) newest = d;
+    }
+    return newest;
+  } catch {
+    return null;
+  }
+}
+
 function isoWeek() {
   const d = new Date();
   const dayNum = d.getUTCDay() || 7;
@@ -309,6 +331,16 @@ if (existsSync(STATE_FILE)) {
     reminders += '- No analytics data imported yet. Run /linkedin:import to start tracking performance.\\n';
   }
 
+  // Trend-store staleness (B-S3): warn-only, ≥7 days. Fires ONLY when the store
+  // already holds captures (newest === null ⇒ no nudge), so a never-scanned user
+  // is never nagged. Neutral wording — "scan for trends" hits trend-spotter's own
+  // trigger; no hardcoded beat (de-niche invariant, §17 guard).
+  const newestTrendCapture = trendsNewestCapture(join(getDataRoot('trends'), 'trends.json'));
+  const daysSinceTrend = daysSince(newestTrendCapture);
+  if (daysSinceTrend !== null && daysSinceTrend >= 7) {
+    reminders += `- Trend signals are ${daysSinceTrend} days old. Scan for trends to refresh the digest before planning content.\\n`;
+  }
+
   // Milestone reminders
   if (milestonePhase && followerCount > 0) {
     if (milestoneStatus === 'SIGNIFICANTLY BEHIND') {