Ignores Cobra's "Additional htlp topics"

### Description

With stock cobra, I can define a command that isn't runnable, and the usage/help shows them under the heading "Additional help topics:". Fang ignores that and puts in the commands section.

### Version

_No response_

### Environment

_No response_

Reproduce the issue with a non-runnable command in stock Cobra and compare its help output with Fang's output. Done means non-runnable commands appear under "Additional help topics:" rather than in the commands section.

Written by the indexing model from the issue text.