Chat: context cell improvements

[beyang]

On a context-less chat request, we show a "none fetched" indicator in the ContextCell, along with a "Resend with current repository context" button:

Clicking "Resend with current repository context" causes the repository chip to be added and the request resent:

The "Resend with current repository context" also appears when context is at-mentioned but there is no repo chip:

This PR also removes the "Edit context" button (which previously caused the fetched context items to be moved to the input), because this was broken and not actually fetching context.

Test plan

Test in local dev the scenarios in the screenshots above.

[vovakulikov]

I tested this in Cody Web in Sourcegraph and it works as expected, left one questions about wierd display:none CSS rule

[vovakulikov]

I think this is wrong; it works because I think the edit button is a Button, and it uses tailwind d-flex class, which overrides display:none here, but just double check what you want to achieve with display none here. Do you want to hide this edit button?

Or it's just a leftover

[vovakulikov]

this PR description description says

"This PR also removes the "Edit context" button "

But I still see edit context / edit results button in JSX, should we just remove it completely from rendering rather than just hide it?

[beyang]

I want to add back the "Edit Context" button soon, and this was the quickest way to do it. I'll submit a follow-up PR to either remove it completely or fix the functionality.

[thenamankumar]

The code looks good.

But I think design may want to have a better UX here: cc @taiyab for design review.

[beyang]

@taiyab happy to consider proposals to improve UX, but this is better than what we have in prod today, so I will merge.

[taiyab]

@thenamankumar @beyang Yea, all good. This is objectively better than existing. We'll bring another iteration to this soon if need be.