ci: add Bun CI workflow

Run tests on Bun runtime across ubuntu and macos. Patches vitest
imports from vite-plus to vanilla vitest since Bun can't use the
vite-plus wrapper.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: killagu

.github/workflows/bun.yml

@@ -0,0 +1,54 @@
+name: Bun CI
+
+on:
+  push:
+    branches: [master]
+  pull_request:
+    branches: [master]
+  merge_group:
+
+jobs:
+  test:
+    strategy:
+      fail-fast: false
+      matrix:
+        os: ['ubuntu-latest', 'macos-latest']
+
+    name: Test (Bun, ${{ matrix.os }})
+    runs-on: ${{ matrix.os }}
+
+    concurrency:
+      group: bun-${{ github.workflow }}-#${{ github.event.pull_request.number || github.head_ref || github.ref }}-(${{ matrix.os }})
+      cancel-in-progress: true
+
+    steps:
+      - uses: actions/checkout@v6
+
+      - uses: oven-sh/setup-bun@v2
+        with:
+          bun-version: latest
+
+      - uses: actions/setup-node@v6
+        with:
+          node-version: '22'
+
+      - uses: pnpm/action-setup@v4
+
+      - run: pnpm install --frozen-lockfile
+
+      - name: Patch vitest imports
+        run: |
+          for f in test/*.test.ts; do
+            [ -e "$f" ] || exit 0
+            sed --version >/dev/null 2>&1 && \
+              sed -i "s@'vite-plus/test'@'vitest'@g" "$f" || \
+              sed -i '' "s@'vite-plus/test'@'vitest'@g" "$f"
+          done
+          sed --version >/dev/null 2>&1 && \
+            sed -i "s@'vite-plus'@'vite'@g" vite.config.ts || \
+            sed -i '' "s@'vite-plus'@'vite'@g" vite.config.ts
+          jq 'del(.overrides) | del(.pnpm.overrides)' package.json > package.json.tmp && mv package.json.tmp package.json
+          pnpm install -D vitest@latest vite@latest
+
+      - name: Run tests with Bun
+        run: bun --bun ./node_modules/.bin/vitest run --reporter=dot