refactor: extract color constants into src/colors.js

[saumya-30-verma]

What does this PR do?

This PR extracts ANSI colour constants into a dedicated src/colors.js module and updates the existing files to use the shared constants instead of hardcoded ANSI escape sequences.

Type of change

• Bug fix
• New feature / tool
• Documentation update
• Refactor

How to test it

1. Run npm install
2. Run node src/index.js
3. Verify the CLI starts successfully.
4. Interact with the CLI and confirm the coloured output (Agent Thinking, Reason, and Choosing tool) is displayed as before.

Related issues

Closes #43

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[saumya-30-verma]

Hi @HoussemEddineChaouch,

I've completed the requested refactor. When you have time, I'd really appreciate your feedback.

Thank you!

[HoussemEddineChaouch]

Hey @saumya-30-verma, good start, the colors.js
extraction is the right direction 🙌

Two files are missing, help.js and llm.js still have
hardcoded ANSI color codes and weren't updated to
import from colors.js. Please update both to import
from colors.js to keep it consistent across the
whole codebase.

[HoussemEddineChaouch]

@saumya-30-verma !

[saumya-30-verma]

Thanks for the review! I've updated help.js and llm.js to use the shared color constants from colors.js and pushed the requested changes. Please let me know if there's anything else to update.