Keep autocomplete from stealing editor focus

[adamsardo]

Addresses Mudlet/Mudlet#5310.
/claim #5310
/claim Mudlet/Mudlet#5310

Summary:

• keep the editor component as the focused widget while autocomplete is visible
• make the popup menu/list non-focus widgets and avoid activating the popup window
• route editor-origin navigation keys to the autocomplete list, while normal typing/backspace continues through the editor
• preserve legacy popup/list key handling with a recursion guard for forwarded events
• add an autocomplete focus regression test that opens suggestions, types through the editor, and verifies the list does not receive focus

This is intentionally different from #11: it does not call editorComponentRef_->setFocus() when autocomplete closes, so it should not steal focus back if the user already moved focus to another non-edbee widget.

Proof:

The proof GIF is generated from the actual edbee widget. It shows autocomplete opening, Down arrow changing the list selection, and a typed p being inserted into the editor while editor focus remains active and the autocomplete list does not receive focus.

Verification:

• git diff --check
• cmake -S . -B build/codex-qt5 -DBUILD_WITH_QT5=ON -DCMAKE_PREFIX_PATH=/opt/homebrew/opt/qt@5 -DCMAKE_BUILD_TYPE=Debug
• cmake --build build/codex-qt5 --parallel 6
• QT_QPA_PLATFORM=offscreen ./build/codex-qt5/edbee-test/edbee-test (784 passed, 0 failures)

[adamsardo]

Added the missing proof artifact to the PR body: a GIF generated from the actual edbee widget showing autocomplete open while editor focus remains active, Down arrow routing selection to the list, and normal typing still landing in the editor.

I also added the focused regression test to edbee-test; local Qt 5.15.18/offscreen run is now 784 passed, 0 failures.