feat(ci): add on-demand PR build workflow (#2578)

.github/workflows/pr-build.yml

@@ -0,0 +1,69 @@
+name: PR Build
+
+on:
+  pull_request_target:
+    types: [labeled, synchronize]
+
+permissions:
+  contents: read
+  pull-requests: write
+
+jobs:
+  build:
+    if: contains(github.event.pull_request.labels.*.name, 'needs-build')
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          ref: ${{ github.event.pull_request.head.sha }}
+          fetch-depth: 0
+      - uses: actions/setup-go@v5
+        with:
+          go-version: '1.25.x'
+          cache: true
+      - uses: goreleaser/goreleaser-action@v6
+        with:
+          version: '~> v2'
+          args: release --snapshot --clean --config .goreleaser-pr.yml
+      - uses: actions/upload-artifact@v4
+        with:
+          name: task_linux_amd64
+          path: dist/task_linux_amd64.tar.gz
+      - uses: actions/upload-artifact@v4
+        with:
+          name: task_linux_arm64
+          path: dist/task_linux_arm64.tar.gz
+      - uses: actions/upload-artifact@v4
+        with:
+          name: task_darwin_amd64
+          path: dist/task_darwin_amd64.tar.gz
+      - uses: actions/upload-artifact@v4
+        with:
+          name: task_darwin_arm64
+          path: dist/task_darwin_arm64.tar.gz
+      - uses: actions/upload-artifact@v4
+        with:
+          name: task_windows_amd64
+          path: dist/task_windows_amd64.zip
+      - uses: actions/upload-artifact@v4
+        with:
+          name: checksums
+          path: dist/task_checksums.txt
+      - uses: peter-evans/find-comment@v3
+        id: find-comment
+        with:
+          token: ${{ secrets.GH_PAT || github.token }}
+          issue-number: ${{ github.event.pull_request.number }}
+          body-includes: '📦 Build artifacts ready!'
+      - uses: peter-evans/create-or-update-comment@v4
+        with:
+          token: ${{ secrets.GH_PAT || github.token }}
+          comment-id: ${{ steps.find-comment.outputs.comment-id }}
+          issue-number: ${{ github.event.pull_request.number }}
+          body: |
+            ## 📦 Build artifacts ready!
+
+            Download binaries from [this workflow run](${{ github.server_url }}/${{ github.repository }}/actions/runs/${{ github.run_id }}).
+
+            Available platforms: Linux, macOS, Windows (amd64, arm64)
+          edit-mode: replace