Brief emotional-mix guardrails + source on its own line

Composition (Codex's priority — content mix was the louder problem):
- _select_diverse now guards the daily five's emotional tone: at most 1 health,
  at most 2 science+health combined, at most 2 of any topic, distinct sources —
  so at least three of the five are community/culture/animals/environment when
  available. Caps relax (mix, then source) only to fill on thin days.
- Verified live: today's five went to environment x2, health, animals, science.

UI:
- Source moved to its own line below the tags, left-justified, for uniform
  rhythm across hero and tiles (was sometimes trailing the tags, right-aligned).
- Watermark kept as-is (intentionally subtle; liked).

Tests updated for the emotional-mix contract (80 total).

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

goodnews/briefs.py

@@ -148,24 +148,44 @@ def _candidate_articles(
     ).fetchall()
 
 
-def _select_diverse(rows: list[sqlite3.Row], limit: int, max_per_topic: int = 2) -> list[sqlite3.Row]:
-    """Pick up to `limit` items from `rows` (already ranked best-first).
+def _select_diverse(rows: list[sqlite3.Row], limit: int) -> list[sqlite3.Row]:
+    """Pick up to `limit` items for the daily brief (rows ranked best-first).
 
-    Contract:
-    1. Prefer higher-ranked items.
-    2. Source diversity: at most one item per source while other sources remain.
-    3. Topic balance: no more than `max_per_topic` of the same topic while other
-       topics still have candidates — so the five don't cluster (e.g. several
-       medical/science items) when community/culture/animals/environment exist.
-    4. Always fill to `limit` when enough candidates exist: the source and topic
-       caps are relaxed (in that order) only as needed to reach the count.
+    The daily five should feel like *good news*, not a research digest, so the
+    emotional mix is guarded — not just topic count:
+    - at most 1 health item,
+    - at most 2 science+health items combined,
+    - at most 2 of any single topic,
+    - distinct sources.
+    Because science/health are capped at 2 combined, at least three of the five
+    are community/culture/animals/environment whenever those exist — so the page
+    leads with breadth, not clustered medical/science breakthroughs.
+
+    Caps are relaxed (topic first, then source) only as needed to still fill the
+    count on thin days; we never return fewer when candidates exist.
     """
     selected: list[sqlite3.Row] = []
     selected_ids: set = set()
     seen_sources: set = set()
     topic_count: dict = {}
 
-    def consider(enforce_source: bool, enforce_topic: bool) -> None:
+    def add(row: sqlite3.Row) -> None:
+        selected.append(row)
+        selected_ids.add(row["id"])
+        seen_sources.add(row["source_name"])
+        topic_count[row["topic"]] = topic_count.get(row["topic"], 0) + 1
+
+    def emotional_mix_ok(row: sqlite3.Row) -> bool:
+        topic = row["topic"]
+        health = topic_count.get("health", 0)
+        science = topic_count.get("science", 0)
+        if topic == "health" and health >= 1:
+            return False
+        if topic in ("science", "health") and (science + health) >= 2:
+            return False
+        return topic_count.get(topic, 0) < 2
+
+    def fill(enforce_mix: bool, enforce_source: bool) -> None:
         for row in rows:
             if len(selected) >= limit:
                 return
@@ -173,17 +193,13 @@ def _select_diverse(rows: list[sqlite3.Row], limit: int, max_per_topic: int = 2)
                 continue
             if enforce_source and row["source_name"] in seen_sources:
                 continue
-            topic = row["topic"]
-            if enforce_topic and topic_count.get(topic, 0) >= max_per_topic:
+            if enforce_mix and not emotional_mix_ok(row):
                 continue
-            selected.append(row)
-            selected_ids.add(row["id"])
-            seen_sources.add(row["source_name"])
-            topic_count[topic] = topic_count.get(topic, 0) + 1
+            add(row)
 
-    consider(enforce_source=True, enforce_topic=True)    # distinct source, topic-balanced
-    consider(enforce_source=True, enforce_topic=False)   # relax topic cap to fill
-    consider(enforce_source=False, enforce_topic=False)  # relax source too, last resort
+    fill(enforce_mix=True, enforce_source=True)    # balanced mix, distinct sources
+    fill(enforce_mix=False, enforce_source=True)    # relax the mix caps to fill
+    fill(enforce_mix=False, enforce_source=False)   # relax source too, last resort
     return selected