Deep audit pass focused on ad fill, load latency, and reliability.
Contains breaking API changes — see CHANGELOG.md for full migration notes.

Highlights:
- Exponential backoff retries replacing fixed 30s delay (biggest fill-rate win)
- Default maxRetries raised from 1 to 5
- Multicast listener model fixes broken event stream + sequence ads
- Network- and lifecycle-aware load resumer (connectivity_plus)
- Cold-start preloads run in parallel — initialize() no longer blocks
- Rewarded ads default to preloaded for instant show
- App Open ads pre-warm after dismiss
- Race-free generation tokens, error-code-based classification
- App Open lifecycle reactor properly disposed in destroyAds
- Verified end-to-end on iPhone 17 Pro simulator and Android API 36 emulator