test: boot the built app in CI so a blank window fails the build

[killerwolf]

Closes the gap that let #29 through.

The gap

The preload bug fixed in #29 made the app open to a blank window — and every check in CI passed on it:

Check	Why it missed the bug
npm run lint / check	it's valid, well-formatted code
npm run typecheck	import { CHANNELS } from "./ipc-types" is valid TypeScript
npm test	the unit tests never boot Electron
npm run pack	builds the app without launching it

Nothing in the pipeline ever started the app.

What this adds

npm run test:smoke boots the real dist/main.js — not a reimplementation of it — and asserts the renderer actually came up:

• the preload loaded without a preload-error
• contextBridge exposed window.electronAPI
• every key in CHANNELS is present on it, read from the compiled ipc-types, so a channel added to the contract without reaching the renderer fails here too
• #root has content, i.e. React mounted

Runs in CI right after npm run pack, which has already produced dist/.

Verified to actually fail

A test that can't fail is worthless, so I reintroduced the exact regression (rebuilding the preload with plain tsc) and confirmed it exits 1 with a diagnostic that names the cause:

Smoke test: booting the built app
  ok    the renderer finished loading
  FAIL  the preload script loaded — dist/preload.js: module not found: ./ipc-types
  FAIL  contextBridge exposed window.electronAPI — got undefined
  FAIL  React mounted and rendered — #root is empty
Smoke test failed (3).

Against main as it now stands, it passes all five assertions.

🤖 Generated with Claude Code