Hide Linux titlebar menu chrome

[moteea]

Summary

• hide the Linux primary-window titlebar overlay by keeping Electron's titleBarOverlay object but making it transparent and 1px tall
• strengthen Linux menu suppression by calling both setMenuBarVisibility(false) and removeMenu?.() next to the existing Windows removeMenu() path
• map Linux webview window chrome back to native instead of application-menu, so the renderer no longer reserves application-menu/window-control chrome space

Why

Recent Codex Desktop builds can show a Linux app/menu decoration row or a visible top-right Electron titlebar overlay. Removing the overlay object entirely, or switching the window to frame: false, can crash the Linux build. Keeping the overlay API present while making it visually transparent avoids that crash path while removing the unwanted chrome.

Validation

• node --check scripts/patches/main-process.js
• node --check scripts/patches/webview-assets.js
• node --test scripts/patch-linux-window-ui.test.js
• tests/scripts_smoke.sh

This behavior was also verified manually through a Nix/Home Manager override against Codex Desktop 26.602.71036 on Linux.

[ilysenko]

Current upstream build applies correctly for me: the generated bundle has the transparent 1px Linux titleBarOverlay, Linux removeMenu?.(), and the webview chrome mapping changes Linux back to native.

One thing to tighten before this leaves draft: applyLinuxWindowControlsSafeAreaPatch now has currentInset equal to the default inset because the right safe area is 0. That makes the inset branch a no-op, and the final currentInset check can make future upstream drift look already-applied if upstream keeps applicationMenu:Object.freeze({left:0,right:0}) but changes/removes the chrome-mapping snippets. Since this PR's functional fix depends on those mapping snippets, please track whether the Linux chrome mapping or browser gate was actually found/already in the desired form, and warn if the safe-area bundle is present but neither mapping is recognizable. That keeps future upstream drift visible instead of silently shipping the old Linux application-menu layout.