feat: Support custom response language (#510)

* feat: Support custom response language

* fix: Add default values for response language in config-manager.js

* chore: Update configuration file and add default response language settings

* feat: Support MCP/CLI custom response language

* chore: Update test comments to English for consistency

* docs: Auto-update and format models.md

* chore: fix format

---------

Co-authored-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>
Co-authored-by: Ralph Khreish <35776126+Crunchyman-ralph@users.noreply.github.com>

scripts/modules/task-manager/response-language.js

@@ -0,0 +1,94 @@
+import path from 'path';
+import fs from 'fs';
+import {
+	getConfig,
+	isConfigFilePresent,
+	writeConfig
+} from '../config-manager.js';
+
+function setResponseLanguage(lang, options = {}) {
+	const { mcpLog, projectRoot } = options;
+
+	const report = (level, ...args) => {
+		if (mcpLog && typeof mcpLog[level] === 'function') {
+			mcpLog[level](...args);
+		}
+	};
+
+	let configPath;
+	let configExists = false;
+
+	if (projectRoot) {
+		configPath = path.join(projectRoot, '.taskmasterconfig');
+		configExists = fs.existsSync(configPath);
+		report(
+			'info',
+			`Checking for .taskmasterconfig at: ${configPath}, exists: ${configExists}`
+		);
+	} else {
+		configExists = isConfigFilePresent();
+		report(
+			'info',
+			`Checking for .taskmasterconfig using isConfigFilePresent(), exists: ${configExists}`
+		);
+	}
+
+	if (!configExists) {
+		return {
+			success: false,
+			error: {
+				code: 'CONFIG_MISSING',
+				message:
+					'The .taskmasterconfig file is missing. Run "task-master models --setup" to create it.'
+			}
+		};
+	}
+
+	// Validate response language
+	if (typeof lang !== 'string' || lang.trim() === '') {
+		return {
+			success: false,
+			error: {
+				code: 'INVALID_RESPONSE_LANGUAGE',
+				message: `Invalid response language: ${lang}. Must be a non-empty string.`
+			}
+		};
+	}
+
+	try {
+		const currentConfig = getConfig(projectRoot);
+		currentConfig.global.responseLanguage = lang;
+		const writeResult = writeConfig(currentConfig, projectRoot);
+
+		if (!writeResult) {
+			return {
+				success: false,
+				error: {
+					code: 'WRITE_ERROR',
+					message: 'Error writing updated configuration to .taskmasterconfig'
+				}
+			};
+		}
+
+		const successMessage = `Successfully set response language to: ${lang}`;
+		report('info', successMessage);
+		return {
+			success: true,
+			data: {
+				responseLanguage: lang,
+				message: successMessage
+			}
+		};
+	} catch (error) {
+		report('error', `Error setting response language: ${error.message}`);
+		return {
+			success: false,
+			error: {
+				code: 'SET_RESPONSE_LANGUAGE_ERROR',
+				message: error.message
+			}
+		};
+	}
+}
+
+export default setResponseLanguage;