feat: v0.12.2 —— GitHub Actions 打 deb / rpm（x86_64 + aarch64）

- 新增 .github/workflows/linux-packages.yml（Gitea 不跑，给 GitHub 镜像用）
  推送 / 打 tag / 手动触发 / PR 时编译，并用下面两个脚本打出安装包
- packaging/build-deb.sh：把 make install 的目录打成 .deb（含依赖、README）
- packaging/build-rpm.sh：用 rpmbuild 打成 .rpm（文件布局、%defattr 都设好）
- x86_64 用 ubuntu-22.04 runner，aarch64 用 ubuntu-24.04-arm（公共仓库才有，
  私有仓库里 ARM 那一步失败不影响 x86_64 的包）
- 构建产物上传 artifact；打 tag 时自动生成 SHA256SUMS 并挂到 Release
- README 补「打包（Linux）」一节，.gitignore 忽略本地 dist/*.deb/*.rpm

packaging/build-rpm.sh

@@ -0,0 +1,65 @@
+#!/usr/bin/env bash
+# 把 `make install` 装出来的目录打成 .rpm（用 rpmbuild，不需要 root）
+# 用法: build-rpm.sh <安装树> <版本> <x86_64|aarch64> <输出目录>
+set -euo pipefail
+
+usage() {
+    echo "用法: $0 <安装树> <版本> <x86_64|aarch64> <输出目录>" >&2
+    exit 2
+}
+
+[ $# -eq 4 ] || usage
+
+stage=$(cd "$1" && pwd)
+version=$2
+arch=$3
+mkdir -p "$4"
+out=$(cd "$4" && pwd)
+
+if [ ! -x "$stage/usr/bin/VoiletMark" ]; then
+    echo "安装树里找不到 usr/bin/VoiletMark: $stage" >&2
+    exit 1
+fi
+
+repo=$(cd "$(dirname "$0")/.." && pwd)
+
+work=$(mktemp -d)
+trap 'rm -rf "$work"' EXIT
+
+top=$work/rpmbuild
+mkdir -p "$top/BUILD" "$top/BUILDROOT" "$top/RPMS" "$top/SOURCES" "$top/SPECS" "$top/SRPMS"
+cp -a "$stage" "$top/SOURCES/root"
+find "$top/SOURCES/root" -type d -exec chmod 755 {} +
+install -Dm644 "$repo/README.md" "$top/SOURCES/root/usr/share/doc/voiletmark/README.md"
+
+cat > "$top/SPECS/voiletmark.spec" <<EOF
+Name:        voiletmark
+Version:     $version
+Release:     1
+Summary:     Lightweight cross-platform Markdown editor
+License:     Proprietary
+URL:         https://git.linuxacme.com/liyepan/VoiletMark
+BuildArch:   $arch
+AutoReqProv: yes
+
+%description
+VoiletMark is a Markdown editor built with Qt 5 and C++17. It renders
+Markdown in place, exports PDF, highlights code in 11 languages, edits
+tables directly, shows a folder sidebar with document outline and can
+run Git commands against the opened repository.
+
+%install
+mkdir -p %{buildroot}
+cp -a %{_sourcedir}/root/. %{buildroot}/
+
+%files
+%defattr(-,root,root,-)
+%{_bindir}/VoiletMark
+%{_datadir}/applications/voiletmark.desktop
+%{_datadir}/icons/hicolor/256x256/apps/voiletmark.png
+%{_docdir}/voiletmark/README.md
+EOF
+
+rpmbuild --define "_topdir $top" -bb "$top/SPECS/voiletmark.spec" >/dev/null
+cp "$top/RPMS/$arch"/*.rpm "$out/"
+echo "已生成 $(ls "$out"/*.rpm)"