Run bun test on push and PRs

Adds a GitHub Actions workflow that installs with a frozen lockfile and
runs `bun test` on Ubuntu and Windows. Windows is in the matrix because
the project's primary development environment is Windows; covering it in
CI catches path-handling regressions before they land.

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

Author: cinderblock

.github/workflows/test.yml

@@ -0,0 +1,26 @@
+name: Test
+
+on:
+  push:
+    branches: [master]
+  pull_request:
+    branches: [master]
+
+jobs:
+  test:
+    strategy:
+      fail-fast: false
+      matrix:
+        os: [ubuntu-latest, windows-latest]
+    runs-on: ${{ matrix.os }}
+
+    steps:
+      - uses: actions/checkout@v4
+
+      - uses: oven-sh/setup-bun@v2
+        with:
+          bun-version: latest
+
+      - run: bun install --frozen-lockfile
+
+      - run: bun test