The hotness tick takes only offers whose hot can change: 40,128 to 0 today (#203)

ddiff --git a/server/domain/hotness.js b/server/domain/hotness.js
iindex 0840f42..8bb13fb 100644
---- a/server/domain/hotness.js
++++ b/server/domain/hotness.js
@@@ -15,8 +15,10 @@
   *
   * The same inputs always give the same number (pure function, fixed rounding). Every snapshot
   * stores all of its inputs, so anyone can recompute it (GET /api/v1/offers/:id/hotness).
-- * Snapshots are taken when votes change, on merge/unmerge, on creation, and by the worker for all
-- * active offers at one shared `t` (so the hot list compares numbers computed at the same moment).
++ * Snapshots are taken when votes change, on merge/unmerge, on creation, and by the worker for the
++ * active offers whose hot is not 0, at one shared `t` (so the hot list compares numbers computed at the
++ * same moment). An offer with no net vote has score 0 and so hot 0 at every age: a tick would only
++ * write the same 0 again (5.5M rows a day once imports made 40,000 offers, 2026-11-02).
   */
  const FORMULA = 'hot@1';
  const HOUR = 3600 * 1000;
@@@ -69,9 +71,15 @@ function createHotness({ store, reads }) {
          return formula({ upWeight: snap.up_weight, downWeight: snap.down_weight, firstSeenAt: snap.first_seen_at, t: snap.computed_at });
      }
  
--    /** Worker: snapshot every active canonical offer created in the window, all at the same t. */
++    /**
++     * Worker: snapshot the active canonical offers created in the window whose hot can change with time, all at the
++     * same t. Hot is score / (age + 2)^1.5, so it moves with age only when the score is not 0; an offer whose latest
++     * hot is 0 (no net vote) stays 0 until a vote, which takes its own snapshot. An offer with no snapshot yet is
++     * included, so it gets one.
++     */
      async function tick({ windowDays = 14, t = store.now() } = {}) {
--        const ids = (await db.prepare(`SELECT id FROM deal_offers WHERE status = 'active' AND merged_into IS NULL AND created_at >= ?`).all(t - windowDays * 24 * HOUR)).map((r) => r.id);
++        const ids = (await db.prepare(`SELECT id FROM deal_offers WHERE status = 'active' AND merged_into IS NULL AND created_at >= ?
++                                         AND (hot_latest IS NULL OR hot_latest <> 0)`).all(t - windowDays * 24 * HOUR)).map((r) => r.id);
          await store.tx(async () => { for (const id of ids) await snapshot(id, 'tick', t); });
          // Keep the latest snapshot per offer, every snapshot a vote, merge or creation made in the last 7 days, and the
          // worker's own tick snapshots of the last day. A tick re-snapshots every active offer (about 2,700, every ten
ddiff --git a/test/hotness.test.js b/test/hotness.test.js
iindex f8cc5be..122d976 100644
---- a/test/hotness.test.js
++++ b/test/hotness.test.js
@@@ -99,6 +99,22 @@ const { formula } = require('../server/domain/hotness');
          assert.deepStrictEqual(hots, [...hots].sort((a, b) => b - a));
      });
  
++    await check('the tick skips offers whose hot is 0 (no net vote: 0 at every age); a vote brings one back', async () => {
++        const db = t.ctx.store.db;
++        const Q = await t.submit(poster, { url: 'https://a.example/quiet', title: 'Offer Quiet', price: '7', currency: 'USD' });
++        assert.strictEqual(Number((await db.prepare('SELECT hot_latest FROM deal_offers WHERE id = ?').get(Q.id)).hot_latest), 0, 'created with hot 0');
++        const ticked = async () => Number((await db.prepare("SELECT COUNT(*) AS n FROM deal_hotness_snapshots WHERE offer_id = ? AND reason = 'tick'").get(Q.id)).n);
++        t.clock.advance(HOUR);
++        await t.ctx.worker.tick();
++        assert.strictEqual(await ticked(), 0, 'a tick writes no new 0 for it');
++        await t.get(`/d/${Q.slug}/vote`, { as: users[0], form: { value: 'up' } });
++        t.clock.advance(HOUR);
++        await t.ctx.worker.tick();
++        assert.strictEqual(await ticked(), 1, 'with a vote its hot moves with age, so the tick takes it');
++        const last = await t.ctx.reads.lastSnapshot(Q.id);
++        assert.ok(last.hot > 0 && last.reason === 'tick');
++    });
++
      await check('tick snapshots are kept a day, the others 7 days, and every offer\'s latest always', async () => {
          const db = t.ctx.store.db;
          const Y = await t.submit(poster, { url: 'https://a.example/keep', title: 'Offer Keep', price: '5', currency: 'USD' });