Crisp hero (prefer og:image), 7-card Highlights, no-recycle Replace + session History

- Hero blur fix: brief enrichment now prefers a page's og:image even when a
  feed thumbnail exists (feed thumbs are often tiny; the hero is shown large).
  Verified: BBC hero upgrades to the 1024px share image, ScienceDaily to 1920px.
- Today is now 'Highlights from Today' — hero + 6 (brief size 7), which also
  makes the secondary grid a balanced 3+3 instead of an orphaned 3+1.
- Replace now excludes every article seen this session (a client-side seen-set),
  so it never cycles back to something already shown.
- New session History panel (this tab only, no account): lists everything seen,
  including swapped-away stories, so they stay recoverable. Persistent
  history/favorites are tabled for sign-in later.

Tests: og:image upgrade of an existing feed image (86 total).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

tests/test_enrich.py

@@ -53,3 +53,19 @@ def test_enrich_caches_failure_and_does_not_retry(conn):
     assert r["image_url"] is None and r["image_checked_at"] is not None  # checked, cached
     assert enrich_brief_images(conn, "2026-05-31", fetch=fail) == 0
     assert len(calls) == 1  # not retried once checked
+
+
+def test_enrich_upgrades_existing_feed_image(tmp_path):
+    # A brief item with a (small) feed image should be upgraded to og:image.
+    from goodnews.db import connect as _c, init_db as _i
+    c = _c(":memory:"); _i(c)
+    c.execute("INSERT INTO sources (id,name,feed_url,trust_score) VALUES (1,'S','http://s/f',5)")
+    c.execute("INSERT INTO articles (id,source_id,canonical_url,title,url_hash,image_url) "
+              "VALUES (1,1,'https://bbc.com/x','t1','h1','https://bbc.com/tiny-thumb.jpg')")
+    c.execute("INSERT INTO daily_briefs (id,brief_date,title) VALUES (1,'2026-05-31','B')")
+    c.execute("INSERT INTO daily_brief_items (brief_id,article_id,rank) VALUES (1,1,1)")
+    c.commit()
+    found = enrich_brief_images(c, "2026-05-31", fetch=lambda u: "https://bbc.com/big-og.jpg")
+    assert found == 1
+    assert c.execute("SELECT image_url FROM articles WHERE id=1").fetchone()["image_url"] == "https://bbc.com/big-og.jpg"
+    c.close()