chore(code-mode): remove code-mode smoke test workflow and script

Only needed during cross-platform verification of the packaged code-mode
fix; drop the CI workflow and its acp-smoke.mjs helper now that it's done.

.github/workflows/x-code-mode-smoke.yml

@@ -1,49 +0,0 @@
-name: Code Mode Smoke
-
-# Packages the Electron app on all three OSes and smoke-tests code mode's
-# cross-platform plumbing (adapter staging, engine stripping, ACP handshake,
-# silent-hang startup timeout) — the failure class that previously only
-# surfaced on a colleague's machine. See apps/x/apps/main/scripts/acp-smoke.mjs.
-
-on:
-  pull_request:
-    paths:
-      - 'apps/x/**'
-      - '.github/workflows/x-code-mode-smoke.yml'
-  workflow_dispatch:
-
-jobs:
-  smoke:
-    strategy:
-      fail-fast: false
-      matrix:
-        os: [macos-latest, ubuntu-latest, windows-latest]
-    runs-on: ${{ matrix.os }}
-
-    steps:
-      - name: Checkout code
-        uses: actions/checkout@v6
-
-      - name: Setup pnpm
-        uses: pnpm/action-setup@v6
-        with:
-          version: 10
-
-      - name: Setup Node.js
-        uses: actions/setup-node@v6
-        with:
-          node-version: 24.15.0
-          cache: 'pnpm'
-          cache-dependency-path: 'apps/x/pnpm-lock.yaml'
-
-      - name: Install dependencies
-        run: pnpm install --frozen-lockfile
-        working-directory: apps/x
-
-      - name: Package app (unsigned)
-        run: npm run package
-        working-directory: apps/x/apps/main
-
-      - name: Run code-mode smoke test
-        run: node scripts/acp-smoke.mjs
-        working-directory: apps/x/apps/main