chore(ui): Custom providers drawer design update

[m-rgba]

Description

Design update for custom AI provider drawer.
Updated from master to get updates to the resizeablesidebar component - this was the only meaningful change:
https://github.com/wandb/weave/pull/3892/files#diff-a535af1cfe19d3df5dddc4a1fa596ee756124e9e8caad8dae3b6887b734f1aa0

Before	After

• Updated header area for height and font weight.
• Updated font to use Source Sans Pro / made typography feel right.
• Updated spacing between form elements.
• Made some tweaks to padding and sizing to prevent page overflow when the screen is short.
• Updated padding around the form.
• Adjusted button sizes on the clear buttons to match the inline inputs.
• Added a sample endpoint description to the base URL field.
• Made buttons full width - added submit / edit logic to the text.

Functional changes:

• Used the ResizeablDrawer cause we should probably center around using those for most of these non-peek drawers.
• Added default header and model rows to save on an action for adding a new row.
• Stripped empty headers (similar to the stripping model logic).
• Stripped the trailing / for the baseURL onSubmit (cause I do that all the time other places when I'm setting up custom models and it's annoying to debug).

[github-actions]

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[jwlee64]

im worried this might be confusing,
i used name because putting the token itself here doesnt work
you have to put the name and then add the name and token to the team secrets

[neutralino1]

Maybe your target branch needs to be rebased to master as well. It seems the PR diff is showing many unrelated changes, which makes it hard to review atomically.