ci: validate every member with mcpp 2026.9.29.5; latest_mcpp -> 2026.9.29.5

.github/workflows/validate.yml

@@ -402,7 +402,12 @@ env:
   # `artifacts` links with its own closure's line, and `${mcpp.bin_dir}` in an
   # action a member's build program declares is that member's product
   # directory.
-  MCPP_VERSION: "2026.9.29.4"
+  #
+  # 2026.9.29.5 (mcpp-community/mcpp#742): a member's build program is reused
+  # across selections and runs after those of the members it depends on, the
+  # build database plans by configuration, and a build reports each step once
+  # with its outcome while a status line states the build.
+  MCPP_VERSION: "2026.9.29.5"
 
 jobs:
   lint:

index.toml

@@ -139,7 +139,13 @@
 # Moved in the pull request that moves validate.yml's pin to 2026.9.29.4,
 # which runs every member on every platform with it. The release changes no
 # descriptor grammar.
+# ── 2026-09-30: latest_mcpp -> 2026.9.29.5, min_mcpp unchanged ─────────────
+#
+# Moved in the pull request that moves validate.yml's pin to 2026.9.29.5,
+# which runs every member on every platform with it. The release changes no
+# descriptor grammar; the build's human output changes, and no check here
+# reads it.
 [index]
 spec        = "1"
 min_mcpp    = "2026.9.18.3"
-latest_mcpp = "2026.9.29.4"
+latest_mcpp = "2026.9.29.5"