fix: ollama returns io.EOF on Done chunk

[SudoBrendan]

Describe your changes

Returning a zero-value Error response on Done caused consumer of Recv() to process an extra, empty/duplicated message. This previously resulted in printing of things like 'hello' from the LLM as 'helloo' in mods. Done now signals end-of-stream as expected.

Related issue/discussion:

N/A - I can open if desired. Ollama streams currently print the last chunk multiple times (at least for me, locally):

$ mods --version
mods version v1.7.0 (c4461d4)
$ mods "Hi there"

  Hi! 😊

  It's nice to hear from you! What can I do for you today??
$ cat my-jira | mods "Is this epic groomed well?"

NoNo

$ mods --continue-last "what's wrong with the summary?"

Too verbose verbose verbose

Checklist before requesting a review

• I have read CONTRIBUTING.md
  • There is no such file in this repo - it was the first thing I tried to find :( LMK if anything here is not in accordance with this community's standards.
• I have performed a self-review of my code

If this is a feature

N/A - bugfix

• I have created a discussion
• A project maintainer has approved this feature request. Link to comment:

[caarlos0]

I refactored this in #486 - feel free to take a look and comment

I think this will not be needed anymore with that in mind.

Thanks for the PR, though! 🙏🏻