fix(release): M51 r1 —— linux-arm64 改用 ubuntu-22.04-arm（与 x64 同 glibc 2.35 地板）

P2-1：24.04-arm 会给出 2.39 地板，把 Debian 12 / Raspberry Pi OS Bookworm
（2.36）挡在门外，且「arm64 只有 24.04 档」这句前提是错的（同段注释自己就承认
ubuntu-22.04-arm 有效）。改 os 为 ubuntu-22.04-arm，注释改成「与 x64 同地板
（2.35），覆盖 Debian 12 / Ubuntu 22.04 arm64 / RPi OS Bookworm」；
README §3/§4/§7.5/§9 与 release-notes 的 Downloads/Support matrix 全量订正
2.39 → 2.35+，删掉「arm64 地板高于 x64」的对比措辞。槽位名、产物名、六槽位
齐全性检查与打包脚本均未变。

P2-2：rustup target add 步骤改 env TARGET + `rustup target add "$TARGET"`，
并补 shell: bash（此前是全文件唯一没显式 shell 的 run，在 Windows 槽位会落进
pwsh）；Linux 图形栈依赖那步也补了 shell: bash，现在所有 run 都显式 bash、
run 块内零 `${{ }}` 直插。

顺带 nit：host_slot() 报错改回原始 arch token（`riscv64` 不再显示成 None），
README §7.5 宣传的那个用例现在诊断可读。

验证：yaml 结构断言（六槽位 / linux-arm64=ubuntu-22.04-arm / 齐全性循环 6 /
run 块 ${{ }} 零泄漏 / run 步骤全带 shell）、全部 run 块 bash -n、grep 2.39
零残留、host_slot 7 组合注入 + freebsd/riscv64 报错含原名、image_arch 真 exe、
windows-arm64 stub 全流程、架构守卫拦截、linux-arm64 归档两次 sha256 一致
（f949d0f5… 与上一轮相同）、windows-x64 原生回归（冒烟 + sha256sum -c）。

packaging/release-notes.md

@@ -11,7 +11,7 @@ No WebView, no bundled runtime, no JRE download needed to start the launcher its
 | Windows 10/11 x64 | `unlucky-launcher-{{VERSION}}-windows-x64.exe` | single exe, double-click to run |
 | Windows 11 ARM64 | `unlucky-launcher-{{VERSION}}-windows-arm64.exe` | single exe, runs natively on ARM64 Windows |
 | Linux x64 (X11/Wayland) | `unlucky-launcher-{{VERSION}}-linux-x64.tar.gz` | single binary inside, no installer |
-| Linux arm64 (X11/Wayland) | `unlucky-launcher-{{VERSION}}-linux-arm64.tar.gz` | single binary inside; needs glibc 2.39+ |
+| Linux arm64 (X11/Wayland) | `unlucky-launcher-{{VERSION}}-linux-arm64.tar.gz` | single binary inside; needs glibc 2.35+ |
 | macOS 12+ Apple Silicon | `unlucky-launcher-{{VERSION}}-macos-arm64.tar.gz` | single binary inside, no installer |
 | macOS 12+ Intel | `unlucky-launcher-{{VERSION}}-macos-x64.tar.gz` | single binary inside, no installer |
 
@@ -28,7 +28,7 @@ with the download on every platform.
 | macOS 12+ (arm64 / x64) | first class | nothing; unsigned build, see Gatekeeper note |
 | Linux x64, X11 | first class | `libxkbcommon`, `fontconfig`, `libGL` (or software renderer), `libxcb` |
 | Linux x64, Wayland | supported | `wayland-client`, `libxkbcommon`, plus the X11 set for XWayland apps |
-| Linux arm64, X11 | first class | glibc **2.39+** (built on `ubuntu-24.04-arm`, higher than the x64 floor of 2.35), `libxkbcommon`, `fontconfig`, `libGL`, `libxcb` |
+| Linux arm64, X11 | first class | glibc 2.35+ (built on `ubuntu-22.04-arm`, same floor as x64), `libxkbcommon`, `fontconfig`, `libGL`, `libxcb` |
 | Linux arm64, Wayland | supported | the above plus `wayland-client` |
 | Windows 8.1/8/7 | unsupported | baseline was raised to Win10 (decision D21) |
 | Android — Termux + X11 | experimental, not promised | CLI only (build from source), GUI unverified; not part of this release matrix |