fix: QOTD/WOTD freshness — pick within the freshest cohort, not the rotated pool

Both selectors ordered candidates least-recently-shown, then daily.seeded_order()
ROTATED the whole list and took [0] — an arbitrary date-hashed item, undoing the
ordering. Result: repeats (quote id 2 on 6/28+6/29; word "harmony" on 6/25+6/28),
no guarantee a pool item is shown before it recurs.

Fix: daily.freshest(rows) returns the freshest cohort only — every NEVER-shown
item while any remain, else the oldest-shown group. quote/wotd _candidates use it;
seeded_order now picks deterministically WITHIN that cohort. So every pool item is
featured once before any repeat, then cycles oldest-first. Dropped the unused
_NO_REPEAT_POOL window. Tests: no-repeat-until-exhausted (quote + wotd) + a
freshest() unit test. 428 backend tests green.

(Separate follow-up: expand the QOTD pool from 16 → 90+ vetted public-domain
quotes for a longer no-repeat window.)

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

tests/test_wotd.py

@@ -142,3 +142,19 @@ def test_polish_returns_none_with_empty_examples():
         def chat_text(self, m):
             return '{"gloss": "A warm clear gloss.", "examples": []}'
     assert wotd._polish(C(), "serene", "adjective", "x") is None
+
+
+def test_no_repeat_until_pool_exhausted(conn):
+    """Same freshness guarantee as QOTD: every word featured once before any repeat,
+    then the oldest-shown repeats first. (Regression for 'harmony' repeating after 3 days.)"""
+    import datetime
+    for w in ["alpha", "bravo", "charlie", "delta"]:
+        conn.execute("INSERT INTO wotd_pool (word, definition) VALUES (?, 'a definition')", (w,))
+    conn.commit()
+    n = 4
+    d0 = datetime.date(2026, 2, 1)
+    picks = [wotd.pick_daily(conn, feature_date=(d0 + datetime.timedelta(days=i)).isoformat())["pool_id"]
+             for i in range(n)]
+    assert len(set(picks)) == n
+    nxt = (d0 + datetime.timedelta(days=n)).isoformat()
+    assert wotd.pick_daily(conn, feature_date=nxt)["pool_id"] == picks[0]