fix (cli): Parse indented code blocks

[dustinbyrne]

This PR includes two fixes:

1. Indented Code Block Parsing: Updates the markdown parser in Thread.onToken to correctly identify code fences (```) and file comments (<!-- file: -->) even when they are indented (e.g., within lists). This ensures the frontend receives proper metadata for syntax highlighting and other features. Resolves Code block parsing does not expect whitespace before code fences #2281
2. OpenAI Model Filtering: Excludes image-generation models (like dall-e and others containing image) from the list fetched from OpenAI, as they are not relevant for Navie's text-based interactions. Also refactors the exclusion logic slightly for clarity.

[dustinbyrne]

Without the associated front end fix, indented code blocks will render like so:

[dustinbyrne]

With the frontend fix:

[kgilpin]

@dividedmind this is coded and has tests. Should it be merged?

[dividedmind]

@dividedmind this is coded and has tests. Should it be merged?

I dunno, looks ok to me, but it's still marked as draft.