Explain command for a specific file doesn't need codebase variable

[mkennten]

Issue

The codebase variable doesn't add any value to the command in step 10, it is not required to search the codebase to explain a single file.

Where this is

Analyze code using prompts in the Chat view

Step 10:
Enter a prompt in the Chat view that generates an explanation of the Program.cs file.
/explain #codebase Explain the Program.cs file

What it should be

/explain #Program.cs

This command is enough and to the point and uses the least number of tokens.