ci: validate every member with mcpp 2026.9.29.2; latest_mcpp -> 2026.9.29.2; ignore the workspace-root build outputs

mcpp 2026.9.29.1 builds a workspace as one graph per configuration and writes
the build directory, project data, compile database and lock at the workspace
root. 2026.9.29.2 (mcpp-community/mcpp#739) corrects what such a plan reads
from its members, among them a member's own relative [indices].path, which
47 members of this index declare.

Author: Sunrisepeak

.github/workflows/validate.yml

@@ -377,7 +377,23 @@ env:
   # as its floor, and tests/examples/mcpp-plugins builds against it. Engine
   # warnings the members may newly print: W1 to W3 of SPEC-008 (the library
   # interface), warnings only.
-  MCPP_VERSION: "2026.9.28.3"
+  #
+  # 2026.9.29.1 (mcpp-community/mcpp#738) builds a workspace as one graph per
+  # configuration: `mcpp test -p <member>` plans that member and what it
+  # reaches in the workspace's build directory, `target/<triple>/<key>/` at
+  # this repository's root, with the member's products in `bin/<name>/`. The
+  # members' own `tests/examples/*/target/` directories are no longer written.
+  # The directory name no longer hashes a package's own flags, so a member
+  # whose flags differ from another's shares the directory and ninja rebuilds
+  # the commands that changed.
+  #
+  # 2026.9.29.2 (mcpp-community/mcpp#739) reads what a member states about
+  # itself from the member: a member's own relative [indices].path is anchored
+  # at the member, a member whose tests import std is tested with the std
+  # module built, and a member's product directory holds every shared library
+  # of its closure. 2026.9.29.1 is not used here: its sweep refused the 47
+  # members that declare their own [indices].
+  MCPP_VERSION: "2026.9.29.2"
 
 jobs:
   lint:

.gitignore

@@ -1,4 +1,10 @@
 .xlings-index-cache.json
+# The workspace's build directory, project data, compile database and lock:
+# mcpp 2026.9.29.1+ writes them at the workspace root for every member.
+/target/
+/.mcpp/
+/compile_commands.json
+/mcpp.lock
 # example project build/fetch artifacts
 tests/examples/*/target/
 tests/examples/*/.mcpp/

index.toml

@@ -126,7 +126,13 @@
 # registers mcpp.plugins 0.17.0, whose package floor it is. The release changes
 # no descriptor grammar; its `[package] mcpp` key is manifest vocabulary, which
 # an older engine reports as unsupported and ignores.
+# ── 2026-09-29: latest_mcpp -> 2026.9.29.2, min_mcpp unchanged ─────────────
+#
+# Moved in the pull request that moves validate.yml's pin to 2026.9.29.2,
+# which runs every member on every platform with it. 2026.9.29.1 is skipped:
+# it resolved a member's own relative [indices].path against the workspace
+# root. Neither release changes descriptor grammar.
 [index]
 spec        = "1"
 min_mcpp    = "2026.9.18.3"
-latest_mcpp = "2026.9.28.3"
+latest_mcpp = "2026.9.29.2"