Fix #26074: Ensure floating windows resize only when upfront.

[joaotomas007]

Resolves: #26074

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• Each commit's message describes its purpose and effects, and references the issue it resolves
• If changes are extensive, there is a sequence of easily reviewable commits
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• I created a unit test or vtest to verify the changes I made (if applicable)

[cbjeukendrup]

Hi, thanks for the PR! Two things:

• instead of merging the master branch into your branch, we prefer that you rebase your branch on top of the master branch. To do so, run git pull --rebase upstream master; git push -f to rebase on master and then push your updated branch.
• you're modifying third-party code in this PR, namely KDDockWidgets code, rather than MuseScore's own code. In general, we try to avoid that, but in this case it's clearly unavoidable; and with KDDockWidgets we've kind of given up trying not to patch it, because we simply had to. So, no problem with this PR, but you may want to consider checking whether the same problem applies to the latest version of KDDockWidgets at https://github.com/kdab/KDDockWidgets, and submitting a fix there as well, so that even more people than just us can benefit from it :)

[DmitryArefiev]

Tested #26074 on Win10, Mac13.7.2, LinuxUbuntu24.04.2 LTS - FIXED