Add openai as a hard dependency

[cpsievert]

Adds openai as a hard dependency so that a handful of chat providers can be used without an additional install. This also helps avoid a confusing install error when tools are used.

Closes #22

[Copilot]

Pull Request Overview

This PR changes the dependency management by adding openai as a hard dependency so that all chat provider modules no longer require separate installation instructions for openai. Key changes include:

• Adding "openai" to the core dependencies in pyproject.toml.
• Removing redundant installation callout notes and try/except blocks for the openai package in multiple provider files.
• Updating provider extras in pyproject.toml to empty lists for modules that previously listed openai.

Reviewed Changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
pyproject.toml	Adds openai as a hard dependency and updates provider extras to reflect the change.
chatlas/_perplexity.py	Removes openai installation guidance from the documentation callout.
chatlas/_openai.py	Eliminates the try/except ImportError block and related callout notes.
chatlas/_ollama.py	Removes openai installation instructions from documentation callout.
chatlas/_groq.py	Removes redundant openai requirement callouts from documentation.
chatlas/_github.py	Removes openai installation instructions from documentation callout.
chatlas/_databricks.py	Updates the package installation message and removes try/except block for openai.

[Copilot]

Since openai is now a hard dependency, consider adding a comment in pyproject.toml explaining that the provider extras such as 'github', 'groq', 'ollama', etc. are intentionally left empty.

[gadenbuie]

Ooh, I kinda agree with Copilot! That's a first 😄

[gadenbuie]

Looks good, the diff very clearly demonstrates that this is a good choice!