- Add features.json manifest at repo root (single source of truth)
- Implement useFeatureEnabled hook + FeatureGate component
- Add ExperimentalFeaturesCard settings panel with opt-in toggles
- Gate sidebar items: managed-agents, projects, workflows
- Gate settings sections via featureGate descriptor field
- Three tiers: stable (always on), experimental (opt-in), dev (dev-only)
- Global 'Show developer features' toggle for dev tier suppression
- localStorage persistence for user overrides
- Designed for Flutter consumption (JSON manifest, platforms field)
Signed-off-by: Taylor Ho <taylorkmho@gmail.com>
