Chat: show context excluded reason in UI

[abeatrix]

CLOSE https://linear.app/sourcegraph/issue/CODY-3725/if-a-user-specifically-mentions-a-file-but-we-dont-use-it-as-context

Right now, users might not be aware of excluded items unless they open the context list, which can cause a lot of confusion when context items were expected:

This PR adds a new UI component below the Context item list to display more information about the excluded context to address this issue:

Test plan

Updated storybook for the new UI component:

After

User can know about the skipped context without opening the context list.

Before

User will not know about the skipped context unless they have the context list opened (at the bottom of the list):

Changelog

Chat: display a warning in UI when at-mention items were excluded.

[chenkc805]

Thanks Bee!

Can we tweak the copy of the one where user exceeds token limits? Here's what I recommend, assuming we can hyperlink:

• 2 context items were retrieved but not used because they exceed the token limit. Learn more about token limits here.

[chenkc805]

Changes in my above comment. Thanks @abeatrix

[abeatrix]

• were retrieved but not used because they exceed the token limit. Learn more about token limits

@chenkc805 This looks ok?

[chenkc805]

Look great! Approved