Hide the Plasma integration options on non-Linux platforms so the Chromium module does not need fallback access for platform-specific options.
Switch the integration package option to mkPackageOption and document the kdePackages default path with pkgsText. Also tighten the focused NMT test so Darwin does not set the Linux-only option while still asserting that no native host file is produced there.
ungoogled-chromium does not reliably support the default Chrome Web Store update URL workflow, but Home Manager already supports local CRX descriptors via crxPath and version.
Document that Linux users should prefer that path and add a regression test covering pkgs.ungoogled-chromium.
Allow the Google Chrome browser modules to manage Chrome Web Store extensions on Darwin while keeping Linux explicit via assertions, since Home Manager cannot write Chrome's system-managed extension directories there.
Add focused regression tests for the Linux and Darwin branches, update the existing google-chrome coverage, and add a news entry.
Keep the proprietary Chrome extensions option removed, but make dictionaries and nativeMessagingHosts available for the explicit google-chrome, google-chrome-beta, and google-chrome-dev modules.
Add a focused regression test covering dictionary and native host files for all three browser namespaces.
Follow the configured browser package when choosing NativeMessagingHosts paths so chromium overrides to google-chrome install manifests in Chrome's config directory. Keep extension and dictionary handling gated for proprietary Chrome, but always generate native messaging hosts, and cover the override case with a focused regression test.
