Initialized openttd-client repo

GEMINI.md

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+# Development and Debugging Mandates
+
+To ensure technical integrity and accurate implementation of the OpenTTD network protocol (especially JGRPP-specific modifications), the following mandates must be followed by all agents.
+
+## 1. Upstream Source Code Access
+The JGRPP upstream repository MUST be available in the workspace for direct source code analysis. This is critical because the OpenTTD protocol is complex, version-specific, and often requires verifying C++ logic for packet structures, KDF (Key Derivation Function) ordering, and state machine transitions.
+
+### Requirement
+If the folder `OpenTTD-patches` is missing, you MUST clone it immediately before performing any protocol-related tasks:
+
+```bash
+git clone --depth 1 -b jgrpp https://github.com/JGRennison/OpenTTD-patches OpenTTD-patches
+```
+
+## 2. Debugging Workflow
+Before implementing or modifying networking code:
+1.  **Verify Packet IDs:** Search `OpenTTD-patches/src/network/core/tcp_game.h` for the `PacketGameType` enum.
+2.  **Verify Encryption Logic:** Check `OpenTTD-patches/src/network/network_crypto.cpp` for any changes to AEAD or PAKE handling.
+3.  **Verify State Transitions:** Analyze `OpenTTD-patches/src/network/network_server.cpp` and `network_client.cpp` to understand the expected sequence of packets (e.g., when to send `ClientMapOk` or `ClientAck`).
+
+## 3. Engineering Standards
+- **Binary Accuracy:** Never guess packet structures. Always cross-reference with the `Recv_` and `Send_` calls in the C++ source.
+- **Protocol Documentation:** If a new protocol detail is discovered, document it in `docs/PROTOCOL.md`.