docs(CHANGELOG): Add v3.0 release notes with full plugin and UE6 details

- Document all 8 core classes added in the UE plugin
- Document UE6 forward compatibility layer
- Document website redesign and new documentation
- Maintain complete version history from 1.0 to 3.0

Author: POWDER-RANGER

CHANGELOG.md

@@ -2,6 +2,47 @@
 
 All notable changes to the Nine Realities Netcode Model project.
 
+## [3.0] - 2026-06-25
+
+### Unreal Engine Plugin
+- Complete C++ implementation of the N+1 concurrent simulation model as a UE plugin
+- `UN1NetcodeManager` — Central orchestrator with Standalone/Client/Server/ListenServer modes
+- `UN1ClientPrediction` — 4-mode adaptive prediction (Conservative/Balanced/Aggressive/Adaptive)
+- `UN1ServerAuthority` — Authoritative simulation with per-client adaptive snapshots and lag compensation
+- `UN1RollbackEngine` — Rollback + replay with cost estimation, depth limiting, and contiguous input validation
+- `UN1BlendInterpolator` — Smooth correction blending with Linear/SmoothStep/Exponential/CriticalDamping curves
+- `UN1ReconciliationEngine` — 4-strategy reconciliation (FullRollback/StateInterpolation/DeltaCorrection/Adaptive)
+- `UN1NetworkClock` — High-precision sync using Cristian's algorithm with jitter buffering
+- `UN1PredictionBuffer` — Ring buffer storing predicted states and inputs for rollback replay
+- Quantized state serialization (0.01 unit position precision, ~0.002 degree rotation)
+- Delta compression for world snapshots (only changed fields serialized)
+- Full Blueprint support with UCLASS/UFUNCTION/UPROPERTY annotations
+- Editor module (`NineRealitiesNetcodeEditor`) for development tooling
+- Plugin config: `.uplugin`, `Build.cs`, `FilterPlugin.ini`
+
+### UE6 Forward Compatibility
+- `UN1UE6Compatibility` — Runtime engine version detection and feature adaptation
+- UE6 Network Snapshots V2 preparation with UE5 fallback
+- QUIC transport configuration flag (auto-disabled on UE5)
+- NetworkPrediction plugin integration hooks
+- Compile-time macros: `N1_UE6_READY`, `N1_UE5_5_OR_LATER`
+- C++20 standard for UE6 compatibility
+
+### Documentation & Site
+- Completely redesigned GitHub Pages site (dark theme, card-based design)
+- New "Plugin" tab with installation guide, C++/Blueprint quick start, architecture overview
+- New "UE6 Ready" tab with compatibility features, migration path table, and planned features
+- Updated hero section with v3.0 badge and UE6 CTA button
+- Enhanced navigation with NEW/UE6 badges on relevant tabs
+- Updated README with plugin quick start, architecture diagrams, and performance summary
+- Updated ROADMAP with 2026-2027 milestones
+
+### Added
+- `N1UE6Compatibility.h/cpp` — Forward compatibility layer
+- `N1NetcodeEditorModule.h/cpp` — Editor module
+- Full API header files in `Public/Core/`, `Public/Pipeline/`, `Public/UE6/`
+- Implementation files in `Private/Core/`, `Private/Pipeline/`, `Private/UE6/`
+
 ## [2.0] - 2025-11-29
 
 ### Added
@@ -41,4 +82,4 @@ All notable changes to the Nine Realities Netcode Model project.
 
 ## Contributing
 
-Found an issue or want to suggest improvements? [Open an issue](https://github.com/POWDER-RANGER/nine-realities-netcode/issues) or submit a pull request.
+Found an issue or want to suggest improvements? [Open an issue](https://github.com/POWDER-RANGER/nine-realities-netcode/issues) or submit a pull request.