ci: Lighthouse CI budgets on PRs — perf / a11y / SEO / best-practices (closes #13)

.github/workflows/lighthouse.yml

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+name: Lighthouse
+
+# Performance / accessibility / SEO / best-practices budgets on the built site, on every PR.
+# Assertions start as WARNINGS (non-blocking) so we can record a baseline; ratchet them to hard
+# 'error' floors in lighthouserc.json once the numbers are known (#13).
+
+on:
+  pull_request:
+  workflow_dispatch:
+
+permissions:
+  contents: read
+
+jobs:
+  lighthouse:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@df4cb1c069e1874edd31b4311f1884172cec0e10 # v6.0.3
+        with:
+          persist-credentials: false # zizmor: artipacked
+      - name: Install Hugo (extended)
+        run: |
+          HUGO_VERSION="$(cat .hugoversion 2>/dev/null || echo 0.162.1)" # tracks .hugoversion once #15 lands
+          wget -O "${{ runner.temp }}/hugo.deb" \
+            "https://github.com/gohugoio/hugo/releases/download/v${HUGO_VERSION}/hugo_extended_${HUGO_VERSION}_linux-amd64.deb"
+          sudo dpkg -i "${{ runner.temp }}/hugo.deb"
+      - name: Build site
+        env:
+          HUGO_ENVIRONMENT: production
+          TZ: UTC
+        run: hugo --gc --minify --baseURL "/"
+      - name: Lighthouse CI
+        uses: treosh/lighthouse-ci-action@3e7e23fb74242897f95c0ba9cabad3d0227b9b18 # 12.6.2
+        with:
+          configPath: ./lighthouserc.json
+          uploadArtifacts: true # store HTML reports as a GitHub artifact (no third-party upload)
+          temporaryPublicStorage: false

lighthouserc.json

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+{
+  "ci": {
+    "collect": {
+      "staticDistDir": "./public",
+      "numberOfRuns": 3
+    },
+    "assert": {
+      "//": "Warnings to start (#13): record a baseline from the first runs, then ratchet these to 'error' floors just under it so regressions fail.",
+      "assertions": {
+        "categories:performance": ["warn", { "minScore": 0.9 }],
+        "categories:accessibility": ["warn", { "minScore": 0.95 }],
+        "categories:seo": ["warn", { "minScore": 0.95 }],
+        "categories:best-practices": ["warn", { "minScore": 0.95 }]
+      }
+    }
+  }
+}