Release prep: 0.6.0 and Linux riscv64 release build (#844)

- release.yml: new linux-riscv64 job (ported from GridCraft): cross-compiles on
  ubuntu-24.04 against ports.ubuntu.com riscv64 libs, packages a tar.gz with
  package.sh --formats tar, smoke-tests lightcraft-cli under QEMU. The release
  job needs it, so its tarball lands in the draft and SHA256SUMS.
- packaging/linux/package.sh: CROSS_ARCH/CROSS_TARGET/CROSS_COMPILE/EMULATOR
  support (target dir, cross strip, emulated --version).
- README Downloads and docs/releasing.md list the riscv64 tarball.

Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>

.github/workflows/release.yml

@@ -5,8 +5,9 @@
 # The signing jobs (macOS, Windows) and the draft-release job run in the `release` environment
 # (restricted to the `release` branch), which holds the signing secrets. Every secret is optional:
 # missing ones produce unsigned artifacts and a warning, never a failed build. The jobs that sign
-# nothing (version, Linux, Flatpak, FreeBSD, web) run without it, so a dispatch on any branch is
-# a dry run of them; the release job needs the signed jobs, so a branch run never drafts a release.
+# nothing (version, Linux, Linux riscv64, Flatpak, FreeBSD, web) run without it, so a dispatch on
+# any branch is a dry run of them; the release job needs the signed jobs, so a branch run never
+# drafts a release.
 name: Release
 
 on:
@@ -272,6 +273,79 @@ jobs:
           path: dist/release/*.flatpak
           if-no-files-found: error
 
+  linux-riscv64:
+    name: Linux riscv64
+    needs: version
+    # Cross-compiled on x86_64 (no hosted RISC-V runners) against the runner's own Ubuntu release
+    # from ports.ubuntu.com, so the binaries need that release's glibc (24.04: 2.39). 22.04's
+    # riscv64 ports lag its amd64 updates, which breaks the multiarch install. tar.gz only; the
+    # CLI is smoke-tested under QEMU.
+    runs-on: ubuntu-24.04
+    # No `environment: release`: this job signs nothing, so it gets no release secrets.
+    env:
+      LIGHTCRAFT_VERSION: ${{ needs.version.outputs.version }}
+      LIGHTCRAFT_BUILD_DATE: ${{ needs.version.outputs.date }}
+    steps:
+      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
+      # Fonts (optional build input; required for releases): see craftrules standards/fonts.md.
+      - uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
+        with:
+          repository: storytold/craft-fonts
+          ref: 8dcdacd5153e64560d109541a47d806f26f048c0 # bump deliberately
+          path: craft-fonts
+      - uses: dtolnay/rust-toolchain@686976e191b89faba57d3206551f0f330d8cb249 # stable
+        with:
+          targets: riscv64gc-unknown-linux-gnu
+      - uses: Swatinem/rust-cache@6323deb102c322ba6fcbdcafc7e3dddab59af2b6 # v2.9.2
+        with:
+          key: release-linux-riscv64
+      - name: Apply version override
+        if: inputs.version != ''
+        run: cargo xtask version set "$LIGHTCRAFT_VERSION"
+      - name: Install cross-compilation dependencies
+        run: |
+          . /etc/os-release
+          sudo dpkg --add-architecture riscv64
+          # Pin the existing (archive.ubuntu.com) sources to amd64; riscv64 comes from ports.
+          if [ -f /etc/apt/sources.list.d/ubuntu.sources ]; then
+            sudo sed -i '/^Types: deb/a Architectures: amd64' /etc/apt/sources.list.d/ubuntu.sources
+          fi
+          if [ -f /etc/apt/sources.list ]; then
+            sudo sed -i 's/^deb /deb [arch=amd64] /g' /etc/apt/sources.list
+            sudo sed -i 's/^deb-src /deb-src [arch=amd64] /g' /etc/apt/sources.list
+          fi
+          for suite in "$VERSION_CODENAME" "$VERSION_CODENAME-updates" "$VERSION_CODENAME-security"; do
+            echo "deb [arch=riscv64] http://ports.ubuntu.com/ubuntu-ports $suite main universe restricted multiverse"
+          done | sudo tee /etc/apt/sources.list.d/riscv64.list
+          sudo apt-get update
+          sudo apt-get install -y --no-install-recommends \
+            gcc-riscv64-linux-gnu binutils-riscv64-linux-gnu libc6-dev-riscv64-cross libc6-dev:riscv64 qemu-user \
+            libxkbcommon-dev:riscv64 libwayland-dev:riscv64 libx11-dev:riscv64 libxrandr-dev:riscv64 \
+            libxi-dev:riscv64 libgl1-mesa-dev:riscv64
+      - name: Build and package (tar.gz)
+        env:
+          CRAFT_FONTS_DIR: ${{ github.workspace }}/craft-fonts
+          CRAFT_FONTS_REQUIRED: "1"
+          CARGO_TARGET_RISCV64GC_UNKNOWN_LINUX_GNU_LINKER: riscv64-linux-gnu-gcc
+          PKG_CONFIG_SYSROOT_DIR: /
+          PKG_CONFIG_PATH: /usr/lib/riscv64-linux-gnu/pkgconfig:/usr/share/pkgconfig
+          PKG_CONFIG_ALLOW_CROSS: "1"
+          CROSS_ARCH: riscv64
+          CROSS_TARGET: riscv64gc-unknown-linux-gnu
+          CROSS_COMPILE: riscv64-linux-gnu-
+          EMULATOR: qemu-riscv64
+          QEMU_LD_PREFIX: /usr/riscv64-linux-gnu
+        run: packaging/linux/package.sh --formats tar
+      - name: Check the tarball
+        run: |
+          tar -tzf dist/release/lightcraft-*-linux-riscv64.tar.gz \
+            | grep -E '/bin/lightcraft$|/bin/lightcraft-cli$|/share/applications/ai\.storyteller\.lightcraft\.desktop$'
+      - uses: actions/upload-artifact@cf430e030ddbb5b0abf93d22962f4752f3646cd9 # v7.0.2
+        with:
+          name: release-linux-riscv64
+          path: dist/release/*.tar.gz
+          if-no-files-found: error
+
   freebsd:
     name: FreeBSD x86_64
     needs: version
@@ -368,7 +442,7 @@ jobs:
 
   release:
     name: Draft GitHub Release
-    needs: [version, macos, windows, linux, flatpak, freebsd, web]
+    needs: [version, macos, windows, linux, linux-riscv64, flatpak, freebsd, web]
     runs-on: ubuntu-latest
     environment: release
     permissions: