fix: anchor Day N to each round's first game instead of lazy first sighting

The banner read "Day 1 of ~60" on day 2 of the playoffs because the old
anchor recorded whatever date we first polled a playoff game as Day 1.
Now round start dates come from /v1/schedule/playoff-series, so Day N
is authoritative and resets at each round boundary. Drops the noisy
"of ~60" denominator.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

app/playoff.py

@@ -173,15 +173,15 @@ def ot_label(period):
     return "OT" if n == 1 else f"{n}OT"
 
 
-def today_meta(raw_games, now=None, day_n=None, day_total=None):
+def today_meta(raw_games, now=None, day_n=None):
     """Build the banner payload from the raw NHL games list.
 
     `raw_games` is the list inside the NHL score response (each with gameType,
     seriesStatus, etc.) — NOT the parsed game dicts. This keeps the dependency
     one-way: playoff.py doesn't need to know parse_games' field names.
 
-    `day_n` / `day_total` are injected by the caller (from the playoff_cache
-    module) to keep this function pure and test-friendly.
+    `day_n` is injected by the caller (from the playoff_cache module) scoped to
+    the max observed round so the banner resets at each round boundary.
     """
     playoff_games = [g for g in raw_games if g.get("gameType") == 3]
     playoff_mode = len(playoff_games) > 0
@@ -191,7 +191,6 @@ def today_meta(raw_games, now=None, day_n=None, day_total=None):
             "playoff_mode": False,
             "round_label": None,
             "day_n": None,
-            "day_total": None,
             "series_active": 0,
             "elimination_count": 0,
             "game7_count": 0,
@@ -218,7 +217,6 @@ def today_meta(raw_games, now=None, day_n=None, day_total=None):
         "playoff_mode": True,
         "round_label": ROUND_LABELS.get(max_round, f"Round {max_round}"),
         "day_n": day_n,
-        "day_total": day_total,
         "series_active": len(series_letters) if series_letters else len(playoff_games),
         "elimination_count": elim,
         "game7_count": g7,