feat(ci): npm publish via OIDC trusted publishing (#4)

Release-triggered publish (plus workflow_dispatch backfill) with provenance, no tokens. Requires the trusted publisher configured on npmjs.com for this repo + publish.yml.

Author: TheStreamCode

.github/workflows/publish.yml

@@ -0,0 +1,47 @@
+name: Publish to npm
+
+on:
+  release:
+    types:
+      - published
+  # Manual backfill (e.g. publishing an existing tag after wiring OIDC).
+  workflow_dispatch:
+
+permissions:
+  contents: read
+  id-token: write
+
+concurrency:
+  group: npm-${{ github.event.release.tag_name || github.run_id }}
+  cancel-in-progress: false
+
+jobs:
+  publish:
+    name: publish
+    runs-on: ubuntu-latest
+    timeout-minutes: 15
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7
+
+      - name: Setup Node.js
+        uses: actions/setup-node@249970729cb0ef3589644e2896645e5dc5ba9c38 # v6
+        with:
+          node-version: 24
+          registry-url: https://registry.npmjs.org/
+          package-manager-cache: false
+
+      - name: Install dependencies
+        run: npm ci
+
+      - name: Verify build and tests
+        run: npm test
+
+      - name: Verify package contents
+        run: npm pack --dry-run
+
+      # OIDC trusted publishing (no tokens): requires the trusted publisher
+      # configured on npmjs.com for this repo + publish.yml workflow.
+      - name: Publish with provenance
+        run: npm publish --access public --provenance