Add a tagged-release CI workflow and Linux/Windows packaging

Pushing a `v*` tag now builds the agent for every supported target and attaches
the archives to a GitHub release. Modelled on the furumi release workflow (a
build matrix, then a publish job that runs `gh release create`), adapted to this
project's two differences: it needs system integration (capabilities/polkit on
Linux, elevation+wintun on Windows, a root daemon on macOS), and its users run
varied distros, not just Ubuntu.

Linux is built as a fully **static musl** binary with cargo-zigbuild, so one
artifact runs on Arch, Alpine, NixOS and old-glibc systems alike, and can be
repackaged into whatever a distro prefers later. musl has no prebuilt
aws-lc-sys bindings, so the Linux jobs install cmake + libclang (bindgen) and
zig (the cross C compiler zigbuild drives). macOS (aarch64) and Windows (x86_64)
build natively; Linux covers x86_64 and aarch64.

Targets: x86_64/aarch64 linux-musl, aarch64 macOS, x86_64 Windows. Each archive
carries the binary, the top-level README, and the platform's install notes plus
integration files:
- dist/linux/: a static-friendly README, a systemd unit (runs as root, so no
  capability grant or polkit rule is needed; a commented non-root variant is
  included), and an install.sh that drops the binary and the unit or prints the
  setcap/polkit alternative.
- dist/windows/: install notes covering wintun.dll and Run-as-administrator.
- dist/macos/: the existing LaunchDaemon plist and notes, now also shipped in
  the archive.

Not exercised yet: the workflow only runs on a real tag push, and the
aws-lc-sys-under-musl build has not been run locally in this session (no zig
toolchain here). YAML and install.sh syntax are validated.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

.github/workflows/release.yml

@@ -0,0 +1,148 @@
+name: Release
+
+# Build the agent for every supported target on a version tag and attach the
+# archives to a GitHub release. Linux is a fully static musl binary (built with
+# cargo-zigbuild) so one artifact runs on any distro — Arch, Alpine, NixOS, old
+# glibc systems alike — and can then be repackaged however a distro prefers.
+on:
+  push:
+    tags: ["v*"]
+
+permissions:
+  contents: read
+
+env:
+  CARGO_TERM_COLOR: always
+  CARGO_NET_RETRY: "10"
+
+jobs:
+  build:
+    name: ${{ matrix.asset }}
+    runs-on: ${{ matrix.os }}
+    strategy:
+      fail-fast: false
+      matrix:
+        include:
+          - os: ubuntu-latest
+            target: x86_64-unknown-linux-musl
+            asset: tsunagi-linux-x86_64
+            archive: tar.gz
+            zig: true
+          - os: ubuntu-latest
+            target: aarch64-unknown-linux-musl
+            asset: tsunagi-linux-aarch64
+            archive: tar.gz
+            zig: true
+          - os: macos-latest
+            target: aarch64-apple-darwin
+            asset: tsunagi-macos-aarch64
+            archive: tar.gz
+            zig: false
+          - os: windows-latest
+            target: x86_64-pc-windows-msvc
+            asset: tsunagi-windows-x86_64
+            archive: zip
+            zig: false
+
+    steps:
+      - uses: actions/checkout@v4
+
+      - uses: dtolnay/rust-toolchain@stable
+        with:
+          targets: ${{ matrix.target }}
+
+      - uses: Swatinem/rust-cache@v2
+        with:
+          key: ${{ matrix.target }}
+
+      # aws-lc-sys (iroh's rustls backend) and the bundled sqlite are C, and the
+      # musl targets have no prebuilt bindings, so bindgen needs libclang and the
+      # C build needs cmake. zig is the cross C compiler cargo-zigbuild drives.
+      - name: Install musl build tooling
+        if: matrix.zig
+        run: sudo apt-get update && sudo apt-get install -y --no-install-recommends cmake clang libclang-dev
+      - name: Install zig
+        if: matrix.zig
+        uses: mlugg/setup-zig@v1
+      - name: Install cargo-zigbuild
+        if: matrix.zig
+        uses: taiki-e/install-action@v2
+        with:
+          tool: cargo-zigbuild
+
+      - name: Build
+        shell: bash
+        run: |
+          set -euo pipefail
+          if [[ "${{ matrix.zig }}" == "true" ]]; then
+            cargo zigbuild --release --locked --target "${{ matrix.target }}" --bin tsunagi
+          else
+            cargo build --release --locked --target "${{ matrix.target }}" --bin tsunagi
+          fi
+
+      - name: Package
+        shell: bash
+        run: |
+          set -euo pipefail
+
+          version="${GITHUB_REF_NAME#v}"
+          stage="dist/pkg/${{ matrix.asset }}"
+          mkdir -p "$stage"
+
+          bin="tsunagi"
+          [[ "${{ runner.os }}" == "Windows" ]] && bin="tsunagi.exe"
+          cp "target/${{ matrix.target }}/release/${bin}" "$stage/"
+
+          # The top-level README, plus the per-OS install notes and integration
+          # files, so the archive carries what the platform needs to set up.
+          cp README.md "$stage/"
+          case "${{ runner.os }}" in
+            Linux)
+              cp dist/linux/tsunagi.service dist/linux/install.sh "$stage/"
+              cp dist/linux/README.md "$stage/INSTALL.md"
+              ;;
+            macOS)
+              cp dist/macos/cy.hexor.tsunagi.plist "$stage/"
+              cp dist/macos/README.md "$stage/INSTALL.md"
+              ;;
+            Windows)
+              cp dist/windows/README.md "$stage/INSTALL.md"
+              ;;
+          esac
+
+          archive="${{ matrix.asset }}-${version}.${{ matrix.archive }}"
+          if [[ "${{ matrix.archive }}" == "zip" ]]; then
+            (cd dist/pkg && 7z a "../../${archive}" "${{ matrix.asset }}")
+          else
+            tar -C dist/pkg -czf "${archive}" "${{ matrix.asset }}"
+          fi
+
+      - uses: actions/upload-artifact@v4
+        with:
+          name: ${{ matrix.asset }}
+          path: ${{ matrix.asset }}-*.*
+          if-no-files-found: error
+
+  publish:
+    name: Publish release
+    needs: build
+    runs-on: ubuntu-latest
+    permissions:
+      contents: write
+    steps:
+      - uses: actions/checkout@v4
+
+      - uses: actions/download-artifact@v4
+        with:
+          path: artifacts
+
+      - name: Create release and upload assets
+        env:
+          GH_TOKEN: ${{ github.token }}
+          RELEASE_TAG: ${{ github.ref_name }}
+        run: |
+          set -euo pipefail
+          gh release create "$RELEASE_TAG" artifacts/*/* \
+            --title "tsunagi ${RELEASE_TAG}" \
+            --generate-notes \
+            --verify-tag