fix(web-chat): normalize chat copy to plain text

[G7CNF]

Summary

• force plain-text clipboard output when users copy selected content from chat messages
• prevent rich-text style leakage (e.g. white text from dark UI) when pasting into white-background apps like Google Sheets
• add an E2E regression test for chat copy behavior

Issue

• Fixes Copied chat text has white font color — invisible when pasted into white-background apps #1059

Validation

• node --check src/channels/web/static/app.js
• python3 -m py_compile tests/e2e/scenarios/test_chat.py

[gemini-code-assist]

Summary of Changes

Hello, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request enhances the user experience by standardizing the copy-paste functionality within the web chat interface. It addresses an issue where rich-text formatting could be inadvertently carried over when copying chat messages, leading to inconsistent styling in external applications. By ensuring that only plain text is copied, the change provides a cleaner and more predictable interaction for users, backed by a new E2E test to prevent future regressions.

Highlights

• Clipboard Behavior: Implemented a mechanism to force plain-text clipboard output when users copy selected content from chat messages, preventing rich-text style leakage (e.g., white text from dark UI) when pasting into other applications.
• Testing: Added a new end-to-end regression test to validate the chat copy behavior, ensuring that only plain text is copied to the clipboard.

Changelog

• src/channels/web/static/app.js
  • Added an event listener for the 'copy' event on the 'chat-messages' element to intercept and normalize clipboard data to 'text/plain'.
• tests/e2e/scenarios/test_chat.py
  • Introduced a new asynchronous test function, test_copy_from_chat_forces_plain_text, to programmatically simulate copying chat content and assert that only plain text is stored in the clipboard.

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[gemini-code-assist]

Code Review

This pull request introduces a fix to normalize copied text from chat messages to plain text, preventing rich-text style leakage into other applications. The implementation adds a copy event listener to the chat messages container, which intercepts the copy action, prevents the default behavior, and sets the clipboard data to plain text only. The logic correctly scopes this functionality to selections within the chat area. A new E2E test is also included, which effectively validates the new behavior by simulating a copy event and asserting that only plain text is added to the (mocked) clipboard. The changes are well-implemented and address the described issue effectively.

[zmanian]

Clean UX fix with thorough E2E testing. The copy handler is properly defensive (null checks, containment check, collapsed selection guard). The second commit improving test determinism shows good attention to flaky-test prevention. LGTM.