Add initial Go package and release automation

.github/workflows/go-ci.yml

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+name: Go CI
+
+on:
+  push:
+    branches: [main, master]
+    paths:
+      - 'minipdf-go/**'
+      - '.github/workflows/go-ci.yml'
+      - '.github/workflows/go-release.yml'
+  pull_request:
+    branches: [main, master]
+    paths:
+      - 'minipdf-go/**'
+      - '.github/workflows/go-ci.yml'
+      - '.github/workflows/go-release.yml'
+
+permissions:
+  contents: read
+
+jobs:
+  quality:
+    runs-on: ubuntu-latest
+    defaults:
+      run:
+        working-directory: minipdf-go
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v6
+
+      - name: Setup Go
+        uses: actions/setup-go@v6
+        with:
+          go-version: '1.22.x'
+          cache: false
+
+      - name: Check formatting
+        shell: bash
+        run: test -z "$(gofmt -l .)"
+
+      - name: Vet
+        run: go vet ./...
+
+      - name: Test
+        run: go test ./...
+
+  windows-test:
+    runs-on: windows-latest
+    defaults:
+      run:
+        working-directory: minipdf-go
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v6
+
+      - name: Setup Go
+        uses: actions/setup-go@v6
+        with:
+          go-version: '1.22.x'
+          cache: false
+
+      - name: Test
+        run: go test ./...

.github/workflows/go-release.yml

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+name: Go Release
+
+on:
+  push:
+    tags:
+      - 'minipdf-go/v*'
+  workflow_dispatch:
+    inputs:
+      tag:
+        description: Existing Go module tag to release (for example, minipdf-go/v0.1.0)
+        required: true
+        type: string
+
+permissions:
+  contents: write
+
+concurrency:
+  group: go-release-${{ github.ref_name }}-${{ inputs.tag }}
+  cancel-in-progress: false
+
+jobs:
+  release:
+    runs-on: ubuntu-latest
+    defaults:
+      run:
+        working-directory: minipdf-go
+    env:
+      RELEASE_TAG: ${{ github.event_name == 'workflow_dispatch' && inputs.tag || github.ref_name }}
+
+    steps:
+      - name: Checkout release tag
+        uses: actions/checkout@v6
+        with:
+          ref: ${{ github.event_name == 'workflow_dispatch' && inputs.tag || github.ref }}
+
+      - name: Setup Go
+        uses: actions/setup-go@v6
+        with:
+          go-version: '1.22.x'
+          cache: false
+
+      - name: Validate release tag
+        id: version
+        shell: bash
+        run: |
+          if [[ ! "$RELEASE_TAG" =~ ^minipdf-go/v[0-9]+\.[0-9]+\.[0-9]+([.-][0-9A-Za-z.-]+)?$ ]]; then
+            echo "::error::Tag '$RELEASE_TAG' must match minipdf-go/v<semver>."
+            exit 1
+          fi
+          MODULE_PATH="$(go list -m -f '{{.Path}}')"
+          if [ "$MODULE_PATH" != "github.com/mini-software/MiniPdf/minipdf-go" ]; then
+            echo "::error::Unexpected Go module path '$MODULE_PATH'."
+            exit 1
+          fi
+          VERSION="${RELEASE_TAG#minipdf-go/}"
+          echo "version=$VERSION" >> "$GITHUB_OUTPUT"
+
+      - name: Check formatting
+        shell: bash
+        run: test -z "$(gofmt -l .)"
+
+      - name: Vet
+        run: go vet ./...
+
+      - name: Test
+        run: go test ./...
+
+      - name: Build release archives
+        shell: bash
+        env:
+          VERSION: ${{ steps.version.outputs.version }}
+        run: |
+          mkdir -p dist
+          targets=(
+            windows/amd64
+            windows/arm64
+            linux/amd64
+            linux/arm64
+            darwin/amd64
+            darwin/arm64
+          )
+          for target in "${targets[@]}"; do
+            IFS=/ read -r goos goarch <<< "$target"
+            archive="minipdf_${VERSION}_${goos}_${goarch}"
+            binary="minipdf"
+            if [ "$goos" = "windows" ]; then
+              binary="minipdf.exe"
+            fi
+            mkdir -p "dist/$archive"
+            CGO_ENABLED=0 GOOS="$goos" GOARCH="$goarch" go build \
+              -trimpath \
+              -ldflags="-s -w -X main.version=$VERSION" \
+              -o "dist/$archive/$binary" \
+              ./cmd/minipdf
+            if [ "$goos" = "windows" ]; then
+              (cd "dist/$archive" && zip -q "../$archive.zip" "$binary")
+            else
+              tar -C "dist/$archive" -czf "dist/$archive.tar.gz" "$binary"
+            fi
+            rm -rf "dist/$archive"
+          done
+          (cd dist && sha256sum minipdf_* > checksums.txt)
+
+      - name: Verify embedded version
+        shell: bash
+        env:
+          VERSION: ${{ steps.version.outputs.version }}
+        run: |
+          actual="$(go run -ldflags="-X main.version=$VERSION" ./cmd/minipdf --version)"
+          if [ "$actual" != "minipdf $VERSION" ]; then
+            echo "::error::CLI reported '$actual'."
+            exit 1
+          fi
+
+      - name: Create GitHub release
+        uses: softprops/action-gh-release@v2
+        with:
+          tag_name: ${{ env.RELEASE_TAG }}
+          name: MiniPdf Go ${{ steps.version.outputs.version }}
+          generate_release_notes: true
+          files: |
+            minipdf-go/dist/*.zip
+            minipdf-go/dist/*.tar.gz
+            minipdf-go/dist/checksums.txt

minipdf-go/README.md

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+# MiniPdf for Go
+
+The experimental native Go implementation of MiniPdf. It provides a reusable
+`minipdf` package and a dependency-free command-line application.
+
+[Project portal](../README.md) | [Rust implementation](../minipdf-rs/README.md) |
+[.NET implementation](../documents/README.nuget.md)
+
+> The Go implementation is an early foundation and is not feature-equivalent
+> with MiniPdf for .NET or Rust. It currently renders basic text from XLSX,
+> DOCX, and PPTX packages. Complex Office layout is not yet supported.
+
+## Requirements
+
+- Go 1.22 or later
+- No Microsoft Office, LibreOffice, Adobe Acrobat, or .NET runtime at runtime
+
+## Library
+
+```go
+package main
+
+import minipdf "github.com/mini-software/MiniPdf/minipdf-go"
+
+func main() {
+	if err := minipdf.ConvertToPDF("report.docx", "report.pdf"); err != nil {
+		panic(err)
+	}
+}
+```
+
+Convert in-memory Office package bytes:
+
+```go
+pdf, err := minipdf.ConvertBytesToPDF(input)
+```
+
+Override the output page size:
+
+```go
+size, err := minipdf.NewPageSize(400, 500)
+if err != nil {
+	panic(err)
+}
+pdf, err := minipdf.ConvertBytesToPDFWithOptions(input, minipdf.ConversionOptions{
+	PageSize: &size,
+})
+```
+
+## Command Line
+
+```powershell
+go install github.com/mini-software/MiniPdf/minipdf-go/cmd/minipdf@latest
+minipdf report.docx
+minipdf data.xlsx -o data.pdf
+minipdf slides.pptx --paper-size a4
+minipdf convert report.docx --page-width 400 --page-height 500
+```
+
+## Current Scope
+
+| Capability | Go status |
+|---|---|
+| XLSX to PDF | Basic cell text and shared strings |
+| DOCX to PDF | Basic paragraphs, tabs, line breaks, and explicit page breaks |
+| PPTX to PDF | Basic slide text |
+| PDF output | Dependency-free PDF 1.4 writer |
+| Page size | Office geometry, A4/Letter presets, or custom points |
+| Fonts | Registration API reserved; embedding is not implemented yet |
+| Interfaces | Go package and native CLI |
+
+The initial renderer deliberately does not claim support for Office styles,
+images, tables, charts, themes, formulas, merged cells, or font embedding.
+
+## Development
+
+```powershell
+cd minipdf-go
+go fmt ./...
+go vet ./...
+go test ./...
+go run ./cmd/minipdf path\to\input.docx
+```
+
+## Publishing
+
+Go modules are published from Git tags rather than uploaded to a package
+registry. Because this module is in the `minipdf-go` repository subdirectory,
+its tags must include that prefix.
+
+After the release change has been merged to `main`, create and push a semantic
+version tag from the release commit:
+
+```powershell
+git tag minipdf-go/v0.1.0
+git push origin minipdf-go/v0.1.0
+```
+
+The [Go Release workflow](../.github/workflows/go-release.yml) validates the
+module, builds Windows, Linux, and macOS CLI archives for AMD64 and ARM64,
+writes SHA-256 checksums, and creates the GitHub Release. No package registry
+token is required. The public Go module proxy discovers the library from the
+same tag.
+
+Verify the published module:
+
+```powershell
+go list -m github.com/mini-software/MiniPdf/minipdf-go@v0.1.0
+go install github.com/mini-software/MiniPdf/minipdf-go/cmd/minipdf@v0.1.0
+minipdf --version
+```
+
+The workflow can also be run manually for an existing tag. It intentionally
+does not create tags, so a manual run cannot publish an untagged Go module.
+
+## License
+
+[Apache License 2.0](../LICENSE).