ci: GitHub Actions workflow — typecheck + test on push / PR

Runs on every push to master/main and every pull request. Steps:
  1. Install system pandoc (apt) — recipedown / postcard integration
     tests shell out to the binary via runPandoc.
  2. Install bun (latest).
  3. bun install --frozen-lockfile.
  4. bun run typecheck.
  5. bun test.

Concurrency group cancels stale runs when a new commit lands on the
same ref. pandoc-wasm tests skip cleanly when the optional peer dep
isn't installed (which it isn't in CI).

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

Author: ctjlewis

.github/workflows/ci.yml

@@ -0,0 +1,38 @@
+name: CI
+
+on:
+  push:
+    branches: [master, main]
+  pull_request:
+
+# Cancel a previous run if a new commit lands while the prior is in flight.
+concurrency:
+  group: ci-${{ github.ref }}
+  cancel-in-progress: true
+
+jobs:
+  test:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Install pandoc
+        # The integration tests (recipedown, postcard) shell out to the
+        # system pandoc binary. ubuntu-latest ships pandoc 3.x.
+        run: sudo apt-get update && sudo apt-get install -y pandoc
+
+      - name: Pandoc version (sanity)
+        run: pandoc --version | head -1
+
+      - uses: oven-sh/setup-bun@v2
+        with:
+          bun-version: latest
+
+      - name: Install dependencies
+        run: bun install --frozen-lockfile
+
+      - name: Typecheck
+        run: bun run typecheck
+
+      - name: Test
+        run: bun test