Echo Protocol

## Added

- Stage 3: The Original
- Independent Original Echo behavior
- Familiar-location tracking
- Bed, storage, crafting, furnace, doorway, portal, and idle-location markers
- Observing, inhabiting, recognizing, replacing, confronting, and leaving states
- Rare replacement events in familiar locations
- Optional target-only Original text events
- Optional non-lethal confrontation damage
- New administrator commands
- Five new Stage 3 advancements
- Persistent Stage 3 progress and cooldowns

## Improved

- Late-game psychological horror progression
- Safe Echo positioning
- Familiar-location tracking
- Server-authoritative multiplayer privacy
- Persistence of event counters and familiar locations

## Known Limitations

- The Original uses scripted movement rather than advanced navigation
- Familiar locations use bounded heuristics
- Old Mimic advancement progress is not imported retroactively
- Recorded movement routes are not saved across server restarts