filesystem: Windows path rejected when request casing matches neither the configured nor on-disk spelling

When using a local version of the filesystem server on Windows I am getting access denied for paths that are allowed directories on Windows. I was moving to this to get off of my own fork sine a prior PR was merged but it is not in release.

To Reproduce
Steps to reproduce the behavior:

1. Setup some allowed directories on Windows
2. Try and access file with them using a local build of filesystem server

Logs
There are no errors in the logs.

Additional context
Here is an example output of read_file showing the issue.

{
  `path`: `C:\\source\\servers\\src\\fetch\\README.md`
}
Error: Access denied - path outside allowed directories: C:\source\servers\src\fetch\README.md not in c:\source, C:\Users\mgoodner

Start by reproducing the Windows filesystem-server access check with the example path and allowed directories from the issue. Trace the allowed-directory validation and its path-casing behavior; done means an allowed Windows path is accepted when its request casing matches neither the configured nor on-disk spelling, with the existing access-denied behavior preserved for paths outside the allowlist.