fix: Improve workspace detection logic

[Bender-0]

This commit improves the workspace detection logic by first trying to get the workspace from the active text editor. This is more reliable when multiple workspaces are open. It also sets the working directory to the workspace root instead of the .superdesign directory.

[hbmartin]

@Bender-0 SecureDesign has fairly complete workspace detection now, let me know what you think?
https://github.com/hbmartin/secure-design

[Bender-0]

@Bender-0 SecureDesign has fairly complete workspace detection now, let me know what you think? https://github.com/hbmartin/secure-design

@hbmartin Hey! Thanks for sharing your repo. I took a look at your version of customAgentService.ts and it looks fantastic!
I'm really impressed with how you've modernized it, especially switching over to the async vscode.workspace.fs API and abstracting out the model selection logic. Using a SecureStorageService for the API keys is a great call for security too.

These changes make the whole service much cleaner, more secure, and more performant. Awesome work