* refactor(preload): drop the unused raw electron IPC bridge
`@electron-toolkit/preload` was used only to expose `window.electron`,
which hands the renderer unrestricted `ipcRenderer` send/invoke/on for any
channel — bypassing the typed per-domain bridges in `src/preload/api/`.
Nothing consumed it. The only references were the assignment itself, the
web client's empty fallback, and a test asserting that fallback has no
keys — i.e. the web build already ran with it empty.
* chore(build): drop the dangling @electron-toolkit/preload vite exclude
The package is gone from package.json and source; leaving it in the
preload externalizeDeps exclude list points at a package that no longer
resolves.