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/utils/path-utils.js

@@ -0,0 +1,49 @@
+/**
+ * path-utils.js
+ * Utility functions for file path operations in Task Master
+ */
+
+import path from 'path';
+import fs from 'fs';
+
+/**
+ * Finds the absolute path to the tasks.json file based on project root and arguments.
+ * @param {Object} args - Command arguments, potentially including 'projectRoot' and 'file'.
+ * @param {Object} log - Logger object.
+ * @returns {string} - Absolute path to the tasks.json file.
+ * @throws {Error} - If tasks.json cannot be found.
+ */
+export function findTasksJsonPath(args, log) {
+  // Assume projectRoot is already normalized absolute path if passed in args
+  // Or use getProjectRoot if we decide to centralize that logic
+  const projectRoot = args.projectRoot || process.cwd(); 
+  log.info(`Searching for tasks.json within project root: ${projectRoot}`);
+
+  const possiblePaths = [];
+
+  // 1. If a file is explicitly provided relative to projectRoot
+  if (args.file) {
+    possiblePaths.push(path.resolve(projectRoot, args.file));
+  }
+
+  // 2. Check the standard locations relative to projectRoot
+  possiblePaths.push(
+    path.join(projectRoot, 'tasks.json'),
+    path.join(projectRoot, 'tasks', 'tasks.json')
+  );
+
+  log.info(`Checking potential task file paths: ${possiblePaths.join(', ')}`);
+
+  // Find the first existing path
+  for (const p of possiblePaths) {
+    if (fs.existsSync(p)) {
+      log.info(`Found tasks file at: ${p}`);
+      return p;
+    }
+  }
+
+  // If no file was found, throw an error
+  const error = new Error(`Tasks file not found in any of the expected locations relative to ${projectRoot}: ${possiblePaths.join(', ')}`);
+  error.code = 'TASKS_FILE_NOT_FOUND';
+  throw error;
+}