Feat: Added automatic determination of task number based on complexity (#884)

- Added 'defaultNumTasks: 10' to default config, now used in 'parse-prd'
- Adjusted 'parse-prd' and 'expand-task' to:
  - Accept a 'numTasks' value of 0
  - Updated tool and command descriptions
  - Updated prompts to 'an appropriate number of' when value is 0
- Updated 'README-task-master.md' and 'command-reference.md' docs
- Added more tests for: 'parse-prd', 'expand-task' and 'config-manager'

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

tests/unit/config-manager.test.js

@@ -136,6 +136,7 @@ const DEFAULT_CONFIG = {
 	global: {
 		logLevel: 'info',
 		debug: false,
+		defaultNumTasks: 10,
 		defaultSubtasks: 5,
 		defaultPriority: 'medium',
 		projectName: 'Task Master',
@@ -738,5 +739,116 @@ describe('getAllProviders', () => {
 
 // Add tests for getParametersForRole if needed
 
+// --- defaultNumTasks Tests ---
+describe('Configuration Getters', () => {
+	test('getDefaultNumTasks should return default value when config is valid', () => {
+		// Arrange: Mock fs.readFileSync to return valid config when called with the expected path
+		fsReadFileSyncSpy.mockImplementation((filePath) => {
+			if (filePath === MOCK_CONFIG_PATH) {
+				return JSON.stringify({
+					global: {
+						defaultNumTasks: 15
+					}
+				});
+			}
+			throw new Error(`Unexpected fs.readFileSync call: ${filePath}`);
+		});
+		fsExistsSyncSpy.mockReturnValue(true);
+
+		// Force reload to clear cache
+		configManager.getConfig(MOCK_PROJECT_ROOT, true);
+
+		// Act: Call getDefaultNumTasks with explicit root
+		const result = configManager.getDefaultNumTasks(MOCK_PROJECT_ROOT);
+
+		// Assert
+		expect(result).toBe(15);
+	});
+
+	test('getDefaultNumTasks should return fallback when config value is invalid', () => {
+		// Arrange: Mock fs.readFileSync to return invalid config
+		fsReadFileSyncSpy.mockImplementation((filePath) => {
+			if (filePath === MOCK_CONFIG_PATH) {
+				return JSON.stringify({
+					global: {
+						defaultNumTasks: 'invalid'
+					}
+				});
+			}
+			throw new Error(`Unexpected fs.readFileSync call: ${filePath}`);
+		});
+		fsExistsSyncSpy.mockReturnValue(true);
+
+		// Force reload to clear cache
+		configManager.getConfig(MOCK_PROJECT_ROOT, true);
+
+		// Act: Call getDefaultNumTasks with explicit root
+		const result = configManager.getDefaultNumTasks(MOCK_PROJECT_ROOT);
+
+		// Assert
+		expect(result).toBe(10); // Should fallback to DEFAULTS.global.defaultNumTasks
+	});
+
+	test('getDefaultNumTasks should return fallback when config value is missing', () => {
+		// Arrange: Mock fs.readFileSync to return config without defaultNumTasks
+		fsReadFileSyncSpy.mockImplementation((filePath) => {
+			if (filePath === MOCK_CONFIG_PATH) {
+				return JSON.stringify({
+					global: {}
+				});
+			}
+			throw new Error(`Unexpected fs.readFileSync call: ${filePath}`);
+		});
+		fsExistsSyncSpy.mockReturnValue(true);
+
+		// Force reload to clear cache
+		configManager.getConfig(MOCK_PROJECT_ROOT, true);
+
+		// Act: Call getDefaultNumTasks with explicit root
+		const result = configManager.getDefaultNumTasks(MOCK_PROJECT_ROOT);
+
+		// Assert
+		expect(result).toBe(10); // Should fallback to DEFAULTS.global.defaultNumTasks
+	});
+
+	test('getDefaultNumTasks should handle non-existent config file', () => {
+		// Arrange: Mock file not existing
+		fsExistsSyncSpy.mockReturnValue(false);
+
+		// Force reload to clear cache
+		configManager.getConfig(MOCK_PROJECT_ROOT, true);
+
+		// Act: Call getDefaultNumTasks with explicit root
+		const result = configManager.getDefaultNumTasks(MOCK_PROJECT_ROOT);
+
+		// Assert
+		expect(result).toBe(10); // Should fallback to DEFAULTS.global.defaultNumTasks
+	});
+
+	test('getDefaultNumTasks should accept explicit project root', () => {
+		// Arrange: Mock fs.readFileSync to return valid config
+		fsReadFileSyncSpy.mockImplementation((filePath) => {
+			if (filePath === MOCK_CONFIG_PATH) {
+				return JSON.stringify({
+					global: {
+						defaultNumTasks: 20
+					}
+				});
+			}
+			throw new Error(`Unexpected fs.readFileSync call: ${filePath}`);
+		});
+		fsExistsSyncSpy.mockReturnValue(true);
+
+		// Force reload to clear cache
+		configManager.getConfig(MOCK_PROJECT_ROOT, true);
+
+		// Act: Call getDefaultNumTasks with explicit project root
+		const result = configManager.getDefaultNumTasks(MOCK_PROJECT_ROOT);
+
+		// Assert
+		expect(result).toBe(20);
+	});
+});
+
 // Note: Tests for setMainModel, setResearchModel were removed as the functions were removed in the implementation.
 // If similar setter functions exist, add tests for them following the writeConfig pattern.