Add GitHub Pages deploy workflow

On push to main: install with frozen lockfile, type-check with
svelte-check, lint, then build with BASE_PATH set to /<repo-name>
so kit.paths.base produces correct asset URLs under the GH Pages
subdomain. Artifact uploaded via actions/upload-pages-artifact@v3
and deployed via actions/deploy-pages@v4.

Concurrency group 'pages' prevents overlapping deploys from
stepping on each other; cancel-in-progress left off so a queued
deploy from a later commit waits for the earlier one to finish
rather than aborting it mid-upload.

1 files changed, 58 insertions, 0 deletions

diff --git a/.github/workflows/deploy.yml b/.github/workflows/deploy.yml
new file mode 100644
index 0000000..5a5e234
--- /dev/null
+++ b/.github/workflows/deploy.yml
@@ -0,0 +1,58 @@
+name: Deploy to GitHub Pages
+
+on:
+  push:
+    branches: [main]
+  workflow_dispatch:
+
+permissions:
+  contents: read
+  pages: write
+  id-token: write
+
+concurrency:
+  group: pages
+  cancel-in-progress: false
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - uses: pnpm/action-setup@v4
+
+      - uses: actions/setup-node@v4
+        with:
+          node-version: 20
+          cache: pnpm
+
+      - name: Install dependencies
+        run: pnpm install --frozen-lockfile
+
+      - name: Type check
+        run: pnpm run check
+
+      - name: Lint
+        run: pnpm run lint
+
+      - name: Build
+        run: pnpm run build
+        env:
+          BASE_PATH: /${{ github.event.repository.name }}
+
+      - uses: actions/configure-pages@v5
+
+      - uses: actions/upload-pages-artifact@v3
+        with:
+          path: dist
+
+  deploy:
+    needs: build
+    runs-on: ubuntu-latest
+    environment:
+      name: github-pages
+      url: ${{ steps.deployment.outputs.page_url }}
+    steps:
+      - uses: actions/deploy-pages@v4
+        id: deployment