Keep gathering portraits visible in realm overview

[ael-dev3]

What changed

• Keeps every valid in-frame gathering portrait mounted in Realm overview instead of enforcing the 24-marker decorative cap.
• Smoothly reduces only the passive portrait artwork according to local screen density, bounded between 58% and 100%.
• Preserves 44px interactive controls, close-camera collision behavior, outbound reservations, camera behavior, and pointer-inert map gestures.

Why

The former passive collision cap caused gathering portraits to disappear and reappear as the Mini App camera moved or zoomed. At maximum overview this made active gathering feel unstable and difficult to read.

Impact

Gathering activity now remains legible across compact Farcaster WebViews. Dense local clusters compress smoothly without taking touch control away from the map.

Validation

• 2,999 tests across 269 files (npm test -- --maxWorkers=2)
• production build and runtime/asset/Mini App verification (npm run build)
• focused portrait layout and CSS contract coverage
• rendered 390×844 Mini App QA fixture: 68/68 unique in-frame gathering portraits remained mounted across repeated frames; scale range 0.661–1.000; zero duplicate keys; all passive markers pointer-inert

No database, authentication, camera, release-version, or patch-note changes.