Scope dial polish (Codex): hero stays closest-first + visible Clear

- Hero constraint: _pick_lead now runs only within the CLOSEST non-empty section of a
  personalized Brief, so a "gentler" wider-region/world story can never be floated into
  the hero slot above a local one. Only widens if the closest section is empty.
- Dial gains a visible Clear (alongside Change) so a reader never feels locked into
  personalization; "World" stays the keep-home-but-go-global option.

366 tests green.

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

goodnews/api.py

@@ -2236,7 +2236,16 @@ def create_app() -> FastAPI:
                         have.add(a["id"])
         # Lead with a gentle, readable story (charged or paywalled stories stay
         # in the set, just not as the first thing seen).
-        items = _pick_lead(items)
+        if home_country and scope != "world" and items:
+            # Keep "closest first": pick the gentlest hero from ONLY the closest non-empty
+            # section, so _pick_lead can never float a wider-region/world story above a
+            # local one. Wider tiers stay in their order behind it.
+            lead = items[0].get("__section")
+            head = [a for a in items if a.get("__section") == lead]
+            tail = [a for a in items if a.get("__section") != lead]
+            items = _pick_lead(head) + tail
+        else:
+            items = _pick_lead(items)
         return BriefResponse(
             brief_date=data["brief_date"],
             title=data["title"],