- Replace vertical "research ladder" list with a visual tech tree rendered as
connected node badges showing prerequisites and branch structure
- Add `initialField` parameter to `openResearchScreen` to open on a specific
category instead of always defaulting to the first one
- Add "View Research" shortcut button on turn report when a tech completes,
jumping directly to that field
- Add Cerebrai species research video (research-cerebrai.mp4)
