Add missing CI tests + Fix Watchdog racing condition

[Avasam]

• mypy is os and python-version sensitive. Test on all supported combinations
  • If you don't want to run a full matrix, we should at least do oldest + newest python versions supported as to cover the extreme ends of the range.
• Added github action concurrency cancellation
• Added missing runtime tests
• Added missing and sphinx tests. (done in Migrate dependency management to PEP 735 + Add sphinx build CI check #98)
• Fixed and simplified some flaky tests.
• Fixed a potential racing condition in Watchdog

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Edit: Already done in previous PR
I think you should enable Build pull requests for this project in https://app.readthedocs.org/dashboard/pywinctl/edit/
See: https://docs.readthedocs.com/platform/stable/pull-requests.html
(Sphinx test can fail sooner directly in CI, RTD PR validation can catch specifics to RTD)

[Avasam]

I still got the following flakes. They should be addressed eventually, but in the mean time, if a test fail, any Collaborator can just press the "Re-run failed jobs" button.

macOS

https://github.com/Kalmat/PyWinCtl/actions/runs/27644692386/job/81753454477?pr=100#step:7:93

WINDOW PARENT: ('AXApplication', 'TextEdit') True
MENU INFO (WORKING IN WINDOWS 10 AND MACOS, BUT NOT IN WINDOWS 11 NOR LINUX)
    subfillit(nameList[1][i][0], sizeList[1][i][0], posList[1][i][0], attrList[1][i][0] if addItemInfo else [],
  File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/pywinctl/_pywinctl_macos.py", line 1543, in subfillit
    subfillit(submenu, subSize, subPos, subAttr,
  File "/Library/Frameworks/Python.framework/Versions/3.10/lib/python3.10/site-packages/pywinctl/_pywinctl_macos.py", line 1536, in subfillit
    subSize = subSize[j]
IndexError: list index out of range

Linux

Action deadlocked and timed out: https://github.com/Kalmat/PyWinCtl/actions/runs/27644692386/job/81753454508?pr=100#step:6:15
May require additional tracing to debug.

[Kalmat]

Hi again!

I have re-run the tests. Everything went ok in my case.

Previous PR (#99) was ok, but I get some conflicts in this one too (I would resolve them by myself, but I don't have even a clue on what is this all about, my apologies).

Thanks!