Fix Linux overlay click-through

[Hronom]

Summary

• restore click-through overlays on Linux with platform-correct API usage
• pin Electron 42.7.0 because Electron 43 regresses X11 input shaping
• guard Electron major upgrades in Dependabot and document the workaround

Root cause

Electron 43.2.0 retains a full-window X11 input region after setIgnoreMouseEvents(true). The same native probe on Electron 42.7.0 reports the expected 1x1 input region. The Electron X11 implementation appears source-identical between these releases, pointing to an upstream Chromium/build-stack regression.

Upstream report: electron/electron#52456

Validation

• native X11 input-region smoke test on two monitors
• npm test (4 passed)
• npm run build
• Dependabot YAML parse
• npm ls electron --depth=0 resolves Electron 42.7.0
• git diff --check