Reload of local Lambda code fails with non .mjs index

## Problem
After successfully loading a local version of my Lambda code, if I restart VSCode, an error occurs and the code won't reload. I get a warning that the file index.mjs doesn't exist.

## Steps to reproduce the issue

1. Create and upload a node function that is structured with an index.js file (not index.mjs).
2. Go to the AWS toolkit->Lambda section and expand the function (which succeeds with warning)
3. Restart VSCode and repeat step 2
4. Error shows, saying "Failed to load resources"

The following log information is reported:

` 2025-07-13 09:23:01.295 [error] Error:
at ue (c:\Users\eric\.vscode\extensions\amazonwebservices.aws-toolkit-vscode-3.69.0-gd1959b9\dist\src\extensionNode.js:2591:2068)
at c:\Users\eric\.vscode\extensions\amazonwebservices.aws-toolkit-vscode-3.69.0-gd1959b9\dist\src\extensionNode.js:2591:7397
at ce (c:\Users\eric\.vscode\extensions\amazonwebservices.aws-toolkit-vscode-3.69.0-gd1959b9\dist\src\extensionNode.js:2591:6073)
at ee (c:\Users\eric\.vscode\extensions\amazonwebservices.aws-toolkit-vscode-3.69.0-gd1959b9\dist\src\extensionNode.js:2591:5957)
at Object.getChildNodes (c:\Users\eric\.vscode\extensions\amazonwebservices.aws-toolkit-vscode-3.69.0-gd1959b9\dist\src\extensionNode.js:2597:23066)
at R (c:\Users\eric\.vscode\extensions\amazonwebservices.aws-toolkit-vscode-3.69.0-gd1959b9\dist\src\extensionNode.js:2741:17482)
at R.getChildren (c:\Users\eric\.vscode\extensions\amazonwebservices.aws-toolkit-vscode-3.69.0-gd1959b9\dist\src\extensionNode.js:2597:23004)
at R.getChildren (c:\Users\eric\.vscode\extensions\amazonwebservices.aws-toolkit-vscode-3.69.0-gd1959b9\dist\src\extensionNode.js:2499:12102)
at N4.Y (file:///c:/Users/eric/AppData/Local/Programs/Microsoft%20VS%20Code/resources/app/out/vs/workbench/api/node/extensionHostProcess.js:164:89098)
at N4.getChildren (file:///c:/Users/eric/AppData/Local/Programs/Microsoft%20VS%20Code/resources/app/out/vs/workbench/api/node/extensionHostProcess.js:164:85612)
at $q.$getChildren (file:///c:/Users/eric/AppData/Local/Programs/Microsoft%20VS%20Code/resources/app/out/vs/workbench/api/node/extensionHostProcess.js:164:82282)

`

## Expected behavior
The code should reload. Note that this works as expected for functions that do have an index.mjs file, so I suspect it relates to the file extension.

## System details

- OS: Windows
- Visual Studio Code version:
- AWS Toolkit version: 3.69 prelease
- Amazon Q version:

Start by reproducing the reload from the AWS Toolkit Lambda section with a function whose entry file is index.js, then compare it with the working index.mjs case. Inspect the extensionNode.js stack trace and the local Lambda resource-loading path; done means the function reloads after restarting VS Code without reporting that index.mjs is missing.

Written by the indexing model from the issue text.