Saves, replays, and multiplayer

Master: https://github.com/stacksjs/the-settlers-iii-remake/issues/4

Versioned save envelopes and seeded command logs preserve complete simulation state. Online matches run authoritatively in Bun and emit visibility-filtered updates to authenticated clients.

Completion gate

All mandatory child acceptance criteria require verified implementation evidence. Research, compilation, prototype victory, and uploaded but unprocessed binaries are not equivalent to completion. HomeOS integration is independent of supported game platform delivery.

Implementation issues

• https://github.com/stacksjs/the-settlers-iii-remake/issues/92 - Implement complete versioned saves and migration policy
• https://github.com/stacksjs/the-settlers-iii-remake/issues/93 - Make checkpoints survive lifecycle and storage failures
• https://github.com/stacksjs/the-settlers-iii-remake/issues/94 - Implement deterministic replay and state diagnostics
• https://github.com/stacksjs/the-settlers-iii-remake/issues/95 - Implement multiplayer sessions and content negotiation
• https://github.com/stacksjs/the-settlers-iii-remake/issues/96 - Implement authoritative multiplayer simulation
• https://github.com/stacksjs/the-settlers-iii-remake/issues/97 - Implement reconnect, background recovery, and network saves
• https://github.com/stacksjs/the-settlers-iii-remake/issues/98 - Complete cross-platform multiplayer behavior

Dependencies

Work the actual child blocking graph. Do not make this entire epic a blocker for independent work. Sources and exact acceptance criteria are recorded in each child.