ci: validate every member with mcpp 2026.9.28.1; latest_mcpp -> 2026.9.28.1 (#481)

Co-authored-by: speak-agent <248744407+speak-agent@users.noreply.github.com>

Author: speak-agent

.github/workflows/validate.yml

@@ -341,7 +341,23 @@ env:
   # once more after the raise.
   #
   # `index.toml` min_mcpp does not move: no descriptor grammar changed.
-  MCPP_VERSION: "2026.9.26.2"
+  # ── 2026-09-28: raised 2026.9.26.2 -> 2026.9.28.1 ─────────────────────────
+  #
+  # 2026.9.28.1 changes four things a member's build can see
+  # (mcpp-community/mcpp#717-#726): the lib root of a host-module package is
+  # ordered among its own package's units by what it imports; a workspace
+  # root with its own [package] passes its workspace tables to a member it
+  # reaches through a path dependency; two packages may deploy byte-identical
+  # files to one name; and on Windows a program built on an LLVM row uses the
+  # dynamic CRT with the toolset's redistributable placed beside it, the model
+  # the cl row already used, which is also the CRT of vcpkg's default
+  # `x64-windows` triplet and of CMake's default. No descriptor here spells a
+  # CRT flag (a hand-written one that contradicts the model is now refused),
+  # so no descriptor needs a change; the raise is the measurement of that on
+  # every member and platform.
+  #
+  # `index.toml` min_mcpp does not move: no descriptor grammar changed.
+  MCPP_VERSION: "2026.9.28.1"
 
 jobs:
   lint:

index.toml

@@ -108,7 +108,14 @@
 # Moved in the pull request that moves validate.yml's pin and the openkal
 # measurement's pin to 2026.9.26.1, which run every member on every platform
 # with it. The release changes no descriptor grammar.
+# ── 2026-09-28: latest_mcpp -> 2026.9.28.1, min_mcpp unchanged ─────────────
+#
+# Moved in the pull request that moves validate.yml's pin to 2026.9.28.1,
+# which runs every member on every platform with it. The release changes no
+# descriptor grammar. An engine from this release on that a later floor
+# leaves below min_mcpp reports the floor as a closing tip of the command that
+# refreshed the index, not as an error at the start of every command.
 [index]
 spec        = "1"
 min_mcpp    = "2026.9.18.3"
-latest_mcpp = "2026.9.26.1"
+latest_mcpp = "2026.9.28.1"