Feat: added support for non vision models STRIX_DISABLE_IMAGES flag

[RMartires]

Issue link: https://github.com/usestrix/strix/issues/187

Support for non vision models

adding this flag STRIX_DISABLE_IMAGES to allow strix to run on LLM's that do not support images as input

Problem: most cheaper models do not support Vision, for e.g. OpenRouter's free models Solution: to make this possible i am

1. disabling the browser automation tool completely (since it relies mainly on sc's)
2. memory compressor now removes all images from messages
3. screenshots are not sent to the LLM

This flag will reduces costs and improves performance for non-vision models