refactor(mcp): Modularize direct functions in MCP server

Split monolithic task-master-core.js into separate function files within
the mcp-server/src/core/direct-functions/ directory. This change:

- Creates individual files for each direct function implementation
- Moves findTasksJsonPath to a dedicated utils/path-utils.js file
- Converts task-master-core.js to be a simple import/export hub
- Improves maintainability and organization of the codebase
- Reduces potential merge conflicts when multiple developers contribute
- Follows standard module separation patterns

Each function is now in its own self-contained file with clear imports and
focused responsibility, while maintaining the same API endpoints.

mcp-server/src/core/direct-functions/cache-stats.js

@@ -0,0 +1,32 @@
+/**
+ * cache-stats.js
+ * Direct function implementation for retrieving cache statistics
+ */
+
+import { contextManager } from '../context-manager.js';
+
+/**
+ * Get cache statistics for monitoring
+ * @param {Object} args - Command arguments
+ * @param {Object} log - Logger object
+ * @returns {Object} - Cache statistics
+ */
+export async function getCacheStatsDirect(args, log) {
+  try {
+    log.info('Retrieving cache statistics');
+    const stats = contextManager.getStats();
+    return {
+      success: true,
+      data: stats
+    };
+  } catch (error) {
+    log.error(`Error getting cache stats: ${error.message}`);
+    return {
+      success: false,
+      error: {
+        code: 'CACHE_STATS_ERROR',
+        message: error.message || 'Unknown error occurred'
+      }
+    };
+  }
+}