fix(ai): ensure entries are populated when exporting group chat

[CXZHANG0508]

Closes #14647

This PR fixes a bug where exporting an AI chat session initiated via "Chat with group" resulted in an empty entries list in the exported file.

The Fix:
I updated the AiChatComponent constructor logic to prioritize the entries list passed as an argument. The component now falls back to stateManager.getSelectedEntries() only if the passed list is null or empty. This ensures that the correct context is used for export in both "Chat with group" and "Chat with selected entry" modes.

Steps to test

1. Open a library that contains groups and entries.
2. Right-click on a Group in the side panel -> Select "Chat with group".
3. Send a message (e.g., "Summarize") to generate some chat history (even if it errors due to no API key, as long as user messages appear).
4. Click the Export button (select JSON format).
5. Open the exported JSON file.
6. Verify: The "entries" array should now contain the bibliographic data of the papers in that group (previously it was empty []).

Mandatory checks

• I own the copyright of the code submitted and I license it under the MIT license
• I manually tested my changes in running JabRef (always required)
• I added JUnit tests for changes (if applicable)
• I added screenshots in the PR description (if change is visible to the user)
• I described the change in CHANGELOG.md in a way that is understandable for the average user (if change is visible to the user)
• I checked the user documentation: Is the information available and up to date? If not, I created an issue at https://github.com/JabRef/user-documentation/issues or, even better, I submitted a pull request updating file(s) in https://github.com/JabRef/user-documentation/tree/main/en.

[koppor]

Strange code!

When is entries null? Is it a different mode? Is the caller doing something wrong?

[CXZHANG0508]

I realized that while the previous code fixed the "chat with group" issue, it introduced a regression for standard multi-selection.
Specifically, when right-clicking a multi-selection to start a chat, the UI often passes only the single focused row, causing the multi-selection to be lost.
I have now modified the logic to handle both scenarios:

1. It detects if the passed entry is just a subset of the current multi-selection (fixing the right-click issue).
2. It correctly prioritizes the passed entries for Group Chat .
   I believe that if we don't add the option to directly chat with a group when creating a new library, the entries will be empty when exported. However, I think this might be permissible; otherwise, this option should be disabled.

[Siedlerchr]

How can entries be null? I would have thought it's an empty list

[koppor]

See #14651 (comment)

[CXZHANG0508]

@Siedlerchr You are right. I re-verified the behavior. I initially assumed that the conflict resolution between the passed entries and the global selection might lead to a null value in some edge cases. However, when the issue was solved, I see that it consistently results in an empty list[] when no selection is active, not null.
I have removed the unnecessary null check. Thanks!

[calixtus]

Dont use AI to communicate with us.

[CXZHANG0508]

@calixtus OK,I will not use the translator with the function of AI, last week I did my work so that I did not response immediately. Is there any issue with my PR now?

[github-actions]

Your pull request conflicts with the target branch.

Please merge with your code. For a step-by-step guide to resolve merge conflicts, see https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/addressing-merge-conflicts/resolving-a-merge-conflict-using-the-command-line.