fix: keep autocomplete from stealing focus

[wengkit218-pixel]

/claim #5310

This fixes autocomplete stealing focus from the editor, which prevented continued typing.

What changed:

• Keep the autocomplete popup and list from taking focus.
• Forward key presses back to the editor while autocomplete is visible.
• Close autocomplete cleanly on Escape without forcing focus changes.
• Add regression tests for typing, navigation keys, Escape, and sibling widget focus.

Validation:

• cmake -S . -B build -G Ninja -DCMAKE_PREFIX_PATH=C:\msys64\ucrt64\lib\cmake -DBUILD_WITH_QT5=OFF
• cmake --build build --target edbee-test -j 2
• edbee-test.exe

Video demo:

• https://github.com/wengkit218-pixel/edbee-lib/releases/download/mudlet-5310-demo/mudlet-5310-real-screen.mp4

[wengkit218-pixel]

Hi! I submitted this PR 3 days ago to fix the autocomplete focus issue. Just checking if there's any update on the review? This is the upstream fix for Mudlet/Mudlet PR #9335. Let me know if I should make any changes. Thanks!

[wengkit218-pixel]

Hi! I submitted this PR 7 days ago to fix the autocomplete focus stealing issue. Could you please review when you have a chance? Let me know if I should make any changes. Thanks!