Fix autocomplete popup focus handling

[MrNewDelhi]

Summary

• keep the autocomplete menu and list from activating or taking focus
• forward typing from either autocomplete popup widget back to the editor
• preserve list navigation when arrow/page keys are received by the menu

Motivation

This addresses a focus-stealing path related to Mudlet/Mudlet#5310 where continued typing can stop reaching the editor after autocomplete opens.

Testing

• Ran git diff --check in the submodule.
• Could not run a full Mudlet build locally because this macOS environment lacks Homebrew, CMake, Ninja, Qt, and Xcode; Homebrew installation is blocked by missing sudo/admin access.

[MrNewDelhi]

Closing this after noticing the earlier, stronger attempts in #12 and #13, which cover the same focus issue with tests and proof. I do not want to duplicate reviewer effort or compete with those existing bounty attempts. Thanks for the project and sorry for the noise.