docs: add CONTRIBUTING.md and CHANGELOG.md; optimize chat parser allocation

CONTRIBUTING.md: code style, PR process, architecture pointers, packet
handler pattern, key files for new contributors.

CHANGELOG.md: grouped changes since v1.8.1-preview into Performance,
Bug Fixes, Features, Security, and Code Quality sections.

Chat parser: use stack-allocated std::array<char, 256> for typical chat
messages instead of heap-allocated std::string. Only falls back to heap
for messages > 256 bytes. Reduces allocator pressure on high-frequency
chat packet handling.

CONTRIBUTING.md

@@ -0,0 +1,72 @@
+# Contributing to Wowee
+
+## Build Setup
+
+See [BUILD_INSTRUCTIONS.md](BUILD_INSTRUCTIONS.md) for full platform-specific details.
+The short version: CMake + Make on Linux/macOS, MSYS2 on Windows.
+
+```
+cmake -B build -DCMAKE_BUILD_TYPE=Debug
+make -C build -j$(nproc)
+```
+
+## Code Style
+
+- **C++17**. Use `#pragma once` for include guards.
+- Namespaces: `wowee::game`, `wowee::rendering`, `wowee::ui`, `wowee::core`, `wowee::network`.
+- Conventional commit messages in imperative mood:
+  - `feat:` new feature
+  - `fix:` bug fix
+  - `refactor:` code restructuring with no behavior change
+  - `perf:` performance improvement
+- Prefer `constexpr` over `static const` for compile-time data.
+- Mark functions whose return value should not be ignored with `[[nodiscard]]`.
+
+## Pull Request Process
+
+1. Branch from `master`.
+2. Keep commits focused -- one logical change per commit.
+3. Describe *what* changed and *why* in the PR description.
+4. Ensure the project compiles cleanly before submitting.
+5. Manual testing against a WoW 3.3.5a server (e.g. AzerothCore/ChromieCraft) is expected
+   for gameplay-affecting changes.
+
+## Architecture Overview
+
+See [docs/architecture.md](docs/architecture.md) for the full picture. Key namespaces:
+
+| Namespace | Responsibility |
+|---|---|
+| `wowee::game` | Game state, packet handling (`GameHandler`), opcode dispatch |
+| `wowee::rendering` | Vulkan renderer, M2/WMO/terrain, sky system |
+| `wowee::ui` | ImGui windows and HUD (`GameScreen`) |
+| `wowee::core` | Coordinates, math, utilities |
+| `wowee::network` | Connection, `Packet` read/write API |
+
+## Packet Handlers
+
+The standard pattern for adding a new server packet handler:
+
+1. Define a `struct FooData` holding the parsed fields.
+2. Write `void GameHandler::handleFoo(network::Packet& packet)` to parse into `FooData`.
+3. Register it in the dispatch table: `registerHandler(LogicalOpcode::SMSG_FOO, &GameHandler::handleFoo)`.
+
+Helper variants: `registerWorldHandler` (requires `isInWorld()`), `registerSkipHandler` (discard),
+`registerErrorHandler` (log warning).
+
+## Testing
+
+There is no automated test suite. Changes are verified by manual testing against
+WoW 3.3.5a private servers (primarily ChromieCraft/AzerothCore). Classic and TBC
+expansion paths are tested against their respective server builds.
+
+## Key Files for New Contributors
+
+| File | What it does |
+|---|---|
+| `include/game/game_handler.hpp` | Central game state and all packet handler declarations |
+| `src/game/game_handler.cpp` | Packet dispatch registration and handler implementations |
+| `include/network/packet.hpp` | `Packet` class -- the read/write API every handler uses |
+| `include/ui/game_screen.hpp` | Main gameplay UI screen (ImGui) |
+| `src/rendering/m2_renderer.cpp` | M2 model loading and rendering |
+| `docs/architecture.md` | High-level system architecture reference |