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>

ideas.md

@@ -1,3 +1,3 @@
 - Ability to silence some categories temporarily (Maybe a user doesn't even want to see health-related articles, even good ones, so they're not reminded of an ongoing medical issue -- a way to avoid something purposely for a bit)
 - Terms to avoid list (To filter even good news that you'd rather not hear about)
--
+- Favorite/save articles