Scaffold example-typescript: cart/discount library with vitest LCOV coverage

Small idiomatic invoicing/cart library exercising the LCOV parser path via
vitest, with lizard for complexity and a deliberately seeded jscpd
duplication block, per plans/example-repositories-plan.md Phase 1.

Author: tbjers

.github/workflows/coverage.yml

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+name: coverage
+on:
+  push:
+    branches: [main]
+  pull_request:
+permissions:
+  id-token: write   # OIDC → Worker
+  checks: write     # PR Check Run
+jobs:
+  coverage:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - uses: actions/setup-node@v4
+        with:
+          node-version: 22
+          cache: npm
+
+      - run: npm ci
+
+      - run: npm run coverage # writes coverage/lcov.info
+
+      - uses: actions/setup-python@v5
+        with:
+          python-version: '3.x'
+
+      - run: pip install lizard
+
+      - run: python -m lizard src --xml > lizard-report.xml
+
+      - run: npx jscpd . --reporters json --output ./jscpd-report
+
+      - uses: CoverageTracker/coverage-tracker/.github/actions/report@v0.2.0
+        with:
+          worker-url: https://demo.coveragetracker.dev

.gitignore

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+node_modules/
+coverage/
+jscpd-report/
+lizard-report.xml

.jscpd.json

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+{
+  "ignore": [
+    "node_modules/**",
+    "coverage/**",
+    "jscpd-report/**",
+    "package-lock.json",
+    "*.md"
+  ]
+}