fix: Windows spawn, prefab path, preview API, asset deps, error messages; add execute-context resource, tool descriptions, scene/script/asset tools

Bug fixes (verified against Cocos Creator 3.8.8):
- diagnostics: shell:true for .cmd/.bat on Windows (T125/T126)
- prefabs: duplicatePrefab target resolves under assets/ (T420)
- cocos-project: add preview.open candidate for 3.8.8 (T444)
- assets-advanced: detect directory assets in inspectAssetDependencies (T110)
- scene: improve component-not-found errors with compilation hint (T429)

Documentation improvements:
- tool-registry: add enum and injected vars to execute_javascript, path format examples, asset ref limitation note
- resources: add cocos://mcp/execute-context resource with variables, patterns, pitfalls

New tools (core 37->38, full 101->110):
- scene-management: create_scene, query_scene_state (core), copy_paste_node, rename_node, reparent_node
- scripts: create_script with component/plain templates
- prefabs: create_prefab
- assets-advanced: batch_asset_ops, find_unused_assets

lib/diagnostics.js

@@ -68,7 +68,11 @@ function findTsConfig(projectPath, explicitPath) {
 
 function runExec(file, args, cwd) {
   return new Promise((resolve) => {
-    execFile(file, args, { cwd, maxBuffer: 8 * 1024 * 1024 }, (error, stdout, stderr) => {
+    const options = { cwd, maxBuffer: 8 * 1024 * 1024 };
+    if (process.platform === 'win32' && /\.(cmd|bat)$/.test(file)) {
+      options.shell = true;
+    }
+    execFile(file, args, options, (error, stdout, stderr) => {
       resolve({
         code: error && typeof error.code === 'number' ? error.code : 0,
         stdout: stdout || '',