Fix copy button not working for REPL error output

[h-michaelson20]

Description

Fixes the copy button functionality in REPL interactive mode error output sections.

When executing Python code that produces errors in the REPL (e.g., NameError), the copy button in the error output section was unresponsive. The stdout/stderr copy button worked correctly, but the error traceback section copy button had no effect when clicked.

Fixes #40207

Changes

Modified the following:
src/outputs.rs: Fixed context issues in render_output_controls by replacing cx.listener() with simple closures, and added custom button implementation for ErrorOutput that copies/opens the complete error (name + message + traceback)
src/outputs/plain.rs: Made full_text() method public to allow access from button handlers
src/outputs/user_error.rs: Added Clone derive to ErrorView struct and removed a couple pieces of commented code

Why This Matters

The copy button was clearly broken and it is useful to have for REPL workflows. Users could potentially need to copy error messages for a variety of reasons.

Testing

See attached demo for proof that the fix is working as intended. (this is my first ever commit, if there are additional test cases I need to write or run, please let me know!)

Screen.Recording.2025-10-19.at.10.15.06.PM.mov

Release Notes:

• Fixed copy button not working for REPL error output

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[Veykril]

Thanks!

[Veykril]

You'll need to sign the CLA for us to merge this.

[cla-bot]

Thank you for your pull request and welcome to our community. We could not parse the GitHub identity of the following contributors: Henry Michaelson.
This is most likely caused by a git client misconfiguration; please make sure to:

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[cla-bot]

The cla-bot has been summoned, and re-checked this pull request!

[cla-bot]

Thank you for your pull request and welcome to our community. We could not parse the GitHub identity of the following contributors: Henry Michaelson.
This is most likely caused by a git client misconfiguration; please make sure to:

1. check if your git client is configured with an email to sign commits git config --list | grep email
2. If not, set it up using git config --global user.email [email protected]
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[h-michaelson20]

@Veykril Done! Thank you.