docs: new env var entry in README

Author: Guilherme Gibertoni

Server/README.md

@@ -147,6 +147,7 @@ These options apply to the `mcp-for-unity` command (whether run via `uvx`, Docke
 - `UNITY_MCP_HTTP_REMOTE_HOSTED` - Enable remote-hosted mode (`true`, `1`, or `yes`)
 - `UNITY_MCP_DEFAULT_INSTANCE` - Default Unity instance to target (project name, hash, or `Name@hash`)
 - `UNITY_MCP_SKIP_STARTUP_CONNECT=1` - Skip initial Unity connection attempt on startup
+- `UNITY_MCP_LOG_DIR` - Override the rotating server log directory. Default: `%LOCALAPPDATA%\UnityMCP\Logs` (Windows), `~/Library/Application Support/UnityMCP/Logs` (macOS), `$XDG_STATE_HOME/UnityMCP/Logs` (Linux/BSD, defaults to `~/.local/state/UnityMCP/Logs`).
 
 API key authentication (remote-hosted mode):