Fix TiGLConsole startup bug when built under Linux

[svengoldberg]

Description

Console showed warning that spoiles console. Hence, it needed a fresh prompt for users to enter commands.

The warning was printed right after >> which spoiled the "currently entered" command. output() now detects output arriving while idle at the prompt: It removes the prompt line, prints the output in its place, re-inserts a fresh prompt below, and restores any text the user had already typed. showHistory() gets a _isDirty = true so history entries keep the original append-below layout.

Fix #1460

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This fix was co-authored by an AI coding assistant and reviewed/verified by me before submission.

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How Has This Been Tested?

The console in Linux is now directly usable from the start on. There is no different behaviour compared to the current main branch after the first prompt.
Also tested in Windows: As expected, there is no change at all (the issue did not occur here in the first place).

Screenshots, that help to understand the changes(if applicable):

Old behaviour: A fresh prompt (-> enter) was needed

Now, the warning does no longer spoil the console and the users can directly enter commands

Checklist for PR Author:

• Unit or integration test added (if applicable)
• Python interface updated (if applicable)
• Python test added (if Python interface updated)
• Doxygen docstrings added
• ChangeLog.md updated

[github-actions]

PR Reminders

This PR has changes in TIGLCreator/ but not in src/, tests/unittests/, tests/integrationtests/, tests/python/, or bindings/python_internal/. ChangeLog.md has changes.

• ✅ ChangeLog.md updated

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This is an automated reminder from CI

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 73.74%. Comparing base (9c884ed) to head (685f4a4).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1461   +/-   ##
=======================================
  Coverage   73.74%   73.74%           
=======================================
  Files         324      324           
  Lines       28665    28665           
=======================================
  Hits        21140    21140           
  Misses       7525     7525           

Flag	Coverage Δ
unittests	73.74% <ø> (ø)

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