docs: Update all documentation to reflect development stage

COMPREHENSIVE DOCUMENTATION CLEANUP:

DEVELOPER_GUIDE.md:
- Add prominent warning at top (development-ready, NOT production-ready)
- New 'Current Limitations' section with detailed warnings:
  * Non-deterministic execution
  * Single-threaded only
  * Not suitable for networked games
  * No error recovery, limited optimizations
- Change all 'Production Ready' → 'Development Ready' status tags
- BgfxRenderer: Phase 8 complete | Experimental
- UIModule: Phase 7 complete | Experimental
- InputModule: Phase 1-3 complete | Gamepad Phase 2 TODO
- Add 'What GroveEngine IS Good For' section (prototyping, learning, AI-assisted dev)
- Add Production Roadmap section

USER_GUIDE.md:
- Add experimental/development warning with link to README

Module READMEs:
- BgfxRenderer/README.md: Add development stage warning
- InputModule/README.md: Clarify Phase 1-3 complete, gamepad TODO
- UIModule/README.md: Add experimental warning, clarify thread-safe design is for future

All documentation now consistently reflects that GroveEngine is:
✅ Excellent for rapid prototyping and experimentation
⚠️ NOT ready for production games
⚠️ Non-deterministic execution
⚠️ Single-threaded only (for now)

Total changes: 5 files, 62 insertions, 13 deletions

docs/DEVELOPER_GUIDE.md

@@ -2,18 +2,59 @@
 
 **Comprehensive guide for building applications with GroveEngine**
 
+⚠️ **IMPORTANT**: GroveEngine is currently in **development stage** - suitable for prototyping and experimentation, **not production games**. The engine is non-deterministic and optimized for rapid iteration, not stability. See [Current Limitations](#current-limitations) below.
+
 ## Table of Contents
 
-1. [Getting Started](#getting-started)
+1. [Current Limitations](#current-limitations)
-2. [Core System](#core-system)
+2. [Getting Started](#getting-started)
-3. [Available Modules](#available-modules)
+3. [Core System](#core-system)
+4. [Available Modules](#available-modules)
    - [BgfxRenderer - 2D Rendering](#bgfxrenderer---2d-rendering)
    - [UIModule - User Interface](#uimodule---user-interface)
    - [InputModule - Input Handling](#inputmodule---input-handling)
-4. [IIO Topics Reference](#iio-topics-reference)
+5. [IIO Topics Reference](#iio-topics-reference)
-5. [Complete Application Example](#complete-application-example)
+6. [Complete Application Example](#complete-application-example)
-6. [Building Your First Game](#building-your-first-game)
+7. [Building Your First Game](#building-your-first-game)
-7. [Advanced Topics](#advanced-topics)
+8. [Advanced Topics](#advanced-topics)
+
+---
+
+## Current Limitations
+
+⚠️ **GroveEngine is EXPERIMENTAL and NOT production-ready.** Understand these limitations before building with it:
+
+### Non-Deterministic Execution
+- **Module execution order is NOT guaranteed** - modules may run in different orders between frames
+- **Not suitable for networked games** - no deterministic replay or synchronization
+- **Race conditions possible** - only SequentialModuleSystem is currently implemented (single-threaded)
+
+### Development Stage
+- **Optimized for rapid iteration**, not stability
+- **No error recovery** - crashes are not handled gracefully
+- **Limited performance optimizations** - no profiling, memory pooling, or SIMD
+- **Single-threaded only** - ThreadedModuleSystem and MultithreadedModuleSystem are TODO
+
+### Module Limitations
+- **InputModule**: Mouse and keyboard only (gamepad Phase 2 not implemented)
+- **BgfxRenderer**: Basic text rendering only (8x8 bitmap font for debug)
+- **UIModule**: Functional but no advanced layout constraints
+
+### What GroveEngine IS Good For
+✅ **Rapid prototyping** - 0.4ms hot-reload for instant iteration
+✅ **Learning modular architecture** - clean interface-based design
+✅ **AI-assisted development** - 200-300 line modules optimized for Claude Code
+✅ **Experimentation** - test game ideas quickly
+
+### Production Roadmap
+To make GroveEngine production-ready, the following is needed:
+- Deterministic execution guarantees
+- Error recovery and graceful degradation
+- Multi-threaded module systems
+- Performance profiling and optimization
+- Network IO and distributed messaging
+- Complete gamepad support
+- Advanced text rendering
 
 ---
 
@@ -84,7 +125,7 @@ GroveEngine uses a **module-based architecture** with hot-reload support:
 
 ### BgfxRenderer - 2D Rendering
 
-**Status:** ✅ Production Ready (Phase 7-8 complete)
+**Status:** ✅ Development Ready (Phase 8 complete) | ⚠️ Non-deterministic, experimental
 
 Multi-backend 2D renderer using bgfx (DirectX 11/12, OpenGL, Vulkan, Metal).
 
@@ -163,7 +204,7 @@ io->publish("render:camera", std::move(camera));
 
 ### UIModule - User Interface
 
-**Status:** ✅ Production Ready (Phase 7 complete)
+**Status:** ✅ Development Ready (Phase 7 complete) | ⚠️ Experimental
 
 Complete UI widget system with layout, scrolling, and tooltips.
 
@@ -267,9 +308,9 @@ UIModule publishes render commands to BgfxRenderer via `UIRenderer`:
 
 ### InputModule - Input Handling
 
-**Status:** ✅ Production Ready (Phase 1 complete)
+**Status:** ✅ Development Ready (Phase 1-3 complete) | ⚠️ Gamepad Phase 2 TODO
 
-Cross-platform input handling with SDL2 backend (mouse, keyboard, gamepad).
+Cross-platform input handling with SDL2 backend (mouse, keyboard).
 
 #### Features
 

docs/USER_GUIDE.md

@@ -2,6 +2,8 @@
 
 GroveEngine is a C++17 hot-reload module system designed for building modular applications with runtime code replacement capabilities.
 
+⚠️ **IMPORTANT**: GroveEngine is **experimental** and **development-ready**, NOT production-ready. It is non-deterministic and optimized for rapid prototyping. See main [README.md](../README.md#current-status) for full limitations.
+
 ## Table of Contents
 
 1. [Overview](#overview)

modules/BgfxRenderer/README.md

@@ -1,5 +1,7 @@
 # BgfxRenderer Module
 
+⚠️ **Development Stage**: Experimental, non-deterministic. See [main README](../../README.md#current-status) for limitations.
+
 Module de rendu 2D pour GroveEngine, basé sur [bgfx](https://github.com/bkaradzic/bgfx).
 
 ## Features

modules/InputModule/README.md

@@ -1,6 +1,8 @@
 # InputModule
 
-Module de capture et conversion d'événements d'entrée (clavier, souris, gamepad) vers le système IIO de GroveEngine.
+⚠️ **Development Stage**: Phase 1-3 complete (mouse, keyboard). Gamepad support is Phase 2 (TODO). See [main README](../../README.md#current-status).
+
+Module de capture et conversion d'événements d'entrée (clavier, souris) vers le système IIO de GroveEngine.
 
 ## Vue d'ensemble
 

modules/UIModule/README.md

@@ -1,5 +1,7 @@
 # UIModule
 
+⚠️ **Development Stage**: Experimental, part of non-deterministic engine. See [main README](../../README.md#current-status) for limitations.
+
 Complete UI widget system for GroveEngine with layout, scrolling, tooltips, and automatic input handling.
 
 ## Features
@@ -10,7 +12,7 @@ Complete UI widget system for GroveEngine with layout, scrolling, tooltips, and
 - **Retained Mode Rendering**: Widgets cache state, reducing IIO traffic by 85%+
 - **Layer Management**: UI renders on top of game content (layer 1000+)
 - **Hot-Reload Support**: Full state preservation across module reloads
-- **Thread-Safe**: Designed for multi-threaded production architecture
+- **Thread-Safe Design**: Architecture ready for future multi-threaded systems (currently single-threaded only)
 
 ## Quick Start