feat: add stream in defaultCompletionOptions yaml

[uinstinct]

Description

The stream option was missing in config.yaml
Some users using a proxy server may not be streaming the response. Hence we might need this option to be available.

Reference discussion: https://discord.com/channels/1108621136150929458/1375084108677517362/1375447221578895450

Checklist

• [] I've read the contributing guide
• [] The relevant docs, if any, have been updated or created
• [] The relevant tests, if any, have been updated or created

Screenshots

[ For visual changes, include screenshots. Screen recordings are particularly helpful, and appreciated! ]

Tests

1. Run this simple express ollama proxy server
2. Create a model with provider: ollama and apiBase: http://localhost:4000/ollama/ and model: qwen2.5-coder:1.5b
3. add stream: false in the above model's defaultCompletionOptions
4. chat with the model and see that responses work
5. if stream: true, the model will not able to chat

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[sestinj]

thanks for adding the test!