ci: run lint, unit, and build on every pull request

Adds a CI workflow that triggers on pull_request to master and beta and
runs the same npm run test pipeline (lint -> unit -> build) that the
publish workflow runs on push, so the PR gate matches the release gate.
Concurrency is keyed by PR number so a force-push cancels the in-flight
run instead of queueing behind it.

Author: sankhesh

.github/workflows/ci.yml

@@ -0,0 +1,28 @@
+name: CI
+
+on:
+  pull_request:
+    branches:
+      - master
+      - beta
+
+concurrency:
+  group: ci-${{ github.workflow }}-${{ github.event.pull_request.number }}
+  cancel-in-progress: true
+
+jobs:
+  test:
+    name: Lint, unit, build
+    runs-on: ubuntu-24.04
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+      - name: Setup node
+        uses: actions/setup-node@v4
+        with:
+          node-version: 22
+          cache: 'npm'
+      - name: Install dependencies
+        run: npm ci
+      - name: Test
+        run: npm run test