ci: 把引导阶段绑定指名的 glibc 载荷装给它(过渡步骤)

`xim:glibc` 的 `latest` 从 `2.44` 移到了 `2.44.2`。载荷目录按请求**解析成**的版本
命名,而 RuntimeBinding 带的是**声明的**版本 —— 而一个已发布的 mcpp vendor 进自己
沙箱的那份 xlings 仍然声明 `2.44`。于是干净机器装出 `2.44.2`,工具链 fixup 要
`2.44`,构建在编译任何东西之前就停住:

    error: selected RuntimeBinding glibc@2.44 requires payload
           '.../xpkgs/xim-x-glibc/2.44', but it is not installed

⚠️ 在每一台**新**机器上出现,在任何已存在的机器上都不出现 —— 所以开发机看不见。
索引的 `pkgs/g/glibc.lua` 把这次失败逐字记着,并给出规则:
「The index is DATA and the client is a PROGRAM: the consumer ships first。」

## ⚠️ 我先试过 bump xlings,撤回了

把 `XLINGS_VERSION` 提到 2026.8.27.1 会让**沙箱里那份** xlings 被换掉
(mcpp 的 `acquire_xlings_binary` 在 pin 前移时更新它),绑定于是**前移**到
`glibc@2.44.2`,而已经装好的是 `2.44` —— 请求比已装的**更新**。那是更糟的一侧:
接受一个更旧的载荷去回答更新的请求,等于静默用上索引明说
「IT IS NOT THE ONE TO INSTALL」的那份(带 mcpp#484 的 preload 缺陷)。

⇒ 保持 xlings 不动,把缺的那个载荷直接装上。

⭐ 待 mcpp 2026.8.27.1(mcpp-community/mcpp#515)发布后移除:它接受
「版本精化了请求」的已装载荷,从它引导就不需要这一步。

Author: speak-agent

.github/workflows/ci.yml

@@ -78,6 +78,34 @@ jobs:
           else
             xlings install "mcpp@$MCPP_VERSION" -y -g
           fi
+          # ⚠️⚠️ TRANSITION: GIVE THE BOOTSTRAP THE glibc ITS BINDING NAMES.
+          #
+          # `xim:glibc`'s `latest` moved from `2.44` to `2.44.2`. A payload
+          # directory is named after the version a request RESOLVED to, while a
+          # RuntimeBinding carries the version that was DECLARED — and the xlings
+          # a released mcpp vendors into its own sandbox still declares `2.44`.
+          # So a clean machine installs `2.44.2`, the toolchain fixup asks for
+          # `2.44`, and the build stops before anything is compiled:
+          #
+          #     error: selected RuntimeBinding glibc@2.44 requires payload
+          #            '…/xpkgs/xim-x-glibc/2.44', but it is not installed
+          #
+          # ⚠️ On every NEW machine and on none that already existed, which is why
+          # it is invisible from a developer's own. Measured on `main` as readily
+          # as on any branch — the index records the same failure verbatim in
+          # `pkgs/g/glibc.lua` and states the rule it broke: "The index is DATA
+          # and the client is a PROGRAM: the consumer ships first."
+          #
+          # ⭐ REMOVE THIS once a released mcpp resolves it. `mcpp 2026.8.27.1`
+          # accepts an installed payload whose version REFINES the requested one
+          # (`payload_dir_for_version`), so a bootstrap from it needs nothing
+          # here. Until then the missing payload is simply installed.
+          if [ -x "$HOME/.mcpp/registry/bin/xlings" ]; then
+            XLINGS_HOME="$HOME/.mcpp/registry" XLINGS_NON_INTERACTIVE=1 \
+              "$HOME/.mcpp/registry/bin/xlings" install glibc@2.44 -y -g \
+              >/dev/null 2>&1 || true
+            echo "glibc payloads present: $(ls "$HOME/.mcpp/registry/data/xpkgs/xim-x-glibc" 2>/dev/null | tr '\n' ' ')"
+          fi
           mcpp --version
           mcpp self config --mirror GLOBAL
           # ⭐⭐ CROSS-VALIDATION: BUILD THE mcpp UNDER REVIEW AND USE THAT ONE.