Delete upstream workflows

This fork does not ship upstream's releases, and its hosted-runner jobs
never start here.

Claude-Session: https://claude.ai/code/session_01HuMDfgFssPUptYUzgZ6Cp8

.github/workflows/ci.yml

@@ -1,58 +0,0 @@
-name: CI
-
-on:
-  push:
-    branches: [main]
-  pull_request:
-    branches: [main]
-
-jobs:
-  test:
-    name: Test on Node.js ${{ matrix.node-version }}
-    runs-on: ubuntu-latest
-
-    strategy:
-      matrix:
-        node-version: [20.x, 22.x]
-
-    steps:
-      - name: Checkout code
-        uses: actions/checkout@v4
-
-      - name: Setup Node.js ${{ matrix.node-version }}
-        uses: actions/setup-node@v4
-        with:
-          node-version: ${{ matrix.node-version }}
-          cache: 'npm'
-
-      - name: Install dependencies
-        run: npm ci
-
-      - name: Run type check
-        run: npm run typecheck
-
-      - name: Run tests
-        run: npm test
-
-      - name: Build
-        run: npm run build
-
-  lint:
-    name: Lint and Format Check
-    runs-on: ubuntu-latest
-
-    steps:
-      - name: Checkout code
-        uses: actions/checkout@v4
-
-      - name: Setup Node.js
-        uses: actions/setup-node@v4
-        with:
-          node-version: 20.x
-          cache: 'npm'
-
-      - name: Install dependencies
-        run: npm ci
-
-      - name: Run type check
-        run: npm run typecheck