Hero emotional-safety guardrail + calmer card polish

Hero guardrail (core to the promise, not cosmetic):
- New hero.py: the lead story is chosen with a stricter filter than the rest of
  the brief — very low cortisol/ragebait and no grief/medical/violence terms
  (cancer, glioblastoma, death, diagnosis, ...). Such constructive-but-charged
  stories stay among the five; they just never lead by default.
- /api/brief applies user avoid-terms FIRST, then lead_with_gentle, so personal
  boundaries always take precedence over the general guardrail.
- Verified live: the brief no longer leads with a glioblastoma story.

Card polish (per review):
- Secondary cards with no real image are now text-first (no row of empty media
  bands); hero still always shows media or a typographic fallback.
- Inline tuning actions are quiet until hover/focus on pointer devices, and stay
  visible (softer) on touch — less interface machinery.

Tests: hero safety + lead reordering (70 total).

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

goodnews/api.py

@@ -30,6 +30,7 @@ from pydantic import BaseModel
 from . import feeds, queries
 from .db import connect, init_db
 from .filters import filter_articles, prefs_from_json
+from .hero import lead_with_gentle
 from .llm import LocalModelClient
 from .moods import MOODS
 from .taxonomy import FLAVORS, TOPICS
@@ -280,7 +281,11 @@ def create_app() -> FastAPI:
         items = data["items"]
         if not fp.is_empty():
             # MVP: filter the stored brief DOWN; no refill from outside the brief.
+            # Runs before hero selection, so personal avoid-terms take precedence.
             items = filter_articles(items, fp, datetime.now(timezone.utc))
+        # Lead with an emotionally-safe story (constructive-but-charged stories
+        # stay in the five, just not as the first thing seen).
+        items = lead_with_gentle(items)
         return BriefResponse(
             brief_date=data["brief_date"],
             title=data["title"],