CmdPal: Re-organize samples

### Description of the new feature / enhancement

Both the code structure and the in-extension structure need cleanup.

- In the extension:
- Use sections and pages to better group changes.
- Provide some form of link from the in-extension samples to the source code.

- In the source:
- Use folders to organize source files so they better align with the structure of the extension.

### Scenario when this would be used?

DevExp

### Supporting information

_No response_

Start by mapping the existing CmdPal sample source structure against the in-extension sample pages and sections; no specific files or tests are named in the issue. Reorganize both so they align, and add links from each in-extension sample to its source code; done means the samples are grouped clearly and every source location is discoverable.

Written by the indexing model from the issue text.