fix: restore packaged runtimes and ship macOS DMG only

Desktop 0.12.7 omitted OpenCode's offline node_modules because the resource
copier excludes node_modules at its source root. Copy from the parent and
verify every prepared configuration file in the final package. Bundle DSH
session projection with the unpacked Host instead of leaving an ASAR-only
external import, and reject external DeepSeek imports in shipped chunks.

Run packaged OpenCode plugin import and the real DSH UtilityProcess handshake
in Windows x64 CI before removing unpacked output. Add regressions using the
actual electron-builder copier and Vite externalization configuration.

Prepare approved Desktop 0.12.8 notes and change macOS defaults and CI to DMG
only. Update aggregation, website downloads and update readers for 12
installers and 20 assets. Current readers retain historical DMG/ZIP support;
the user accepts that older macOS GitHub readers and all older mirror readers
need manual upgrades. Agent remains 0.11.21, with no new Agent or LoongArch tag.

Validation: 3608 tests passed, 0 failed, 61 skipped across 339 files;
typecheck, lint, release-note validation, website static checks and 18 website
tests passed. No local production build or packaged-app launch was performed
at the user's request; actual packaged startup validation runs in CI.

Release note: 修复安装后 OpenCode 离线依赖缺失和 DeepSeek Harness Host 启动退出；macOS 改为仅提供 DMG，受影响旧版用户需从下载页手动升级。

sites/README.md

@@ -81,7 +81,7 @@ https://github.com/mesalogo/goodbuddy/releases/latest
 
 校验规则与桌面更新检查保持一致：索引只能指向稳定 SemVer 版本，必须恰好
 包含 Windows、macOS、Linux 的 x64 / arm64 六个匹配目标；每个目标必须提供
-准确的两种格式和扩展名、正的安全整数大小、64 字符小写十六进制 SHA-256、
+准确的格式和扩展名（Windows 两种、macOS 仅 DMG、Linux 三种），正的安全整数大小、64 字符小写十六进制 SHA-256、
 全局唯一文件名，以及位于
 `https://goodbuddy.oss-cn-beijing.aliyuncs.com/releases/v${version}/`
 下、对文件名进行 URL 编码的精确地址。校验清单和 GitHub 回退地址也必须
@@ -90,7 +90,7 @@ https://github.com/mesalogo/goodbuddy/releases/latest
 安装包文件名必须与发布生成器完全一致：Windows 使用
 `GoodBuddy-${version}-windows-${arch}-setup.exe` 与
 `GoodBuddy-${version}-windows-${arch}-portable.zip`；macOS 使用
-`GoodBuddy-${version}-mac-${arch}.dmg|zip`；Linux x64 的 AppImage、DEB 与
+`GoodBuddy-${version}-mac-${arch}.dmg`；读取器仍接受历史 DMG/ZIP 清单，但当前页面不提供 macOS ZIP 选项。Linux x64 的 AppImage、DEB 与
 RPM 分别使用 electron-builder 的 `x86_64`、`amd64` 与 `x86_64` 架构名。
 Linux arm64 的 AppImage/DEB 使用 `arm64`，RPM 使用 `aarch64`。
 Linux 处理器选择器另外提供龙芯 `loong64` 实验预览；选中后安装包类型固定为