MIL-011 tasks 2 to 4: the default tools-ref is the current major

code-metrics.yml defaulted tools-ref to v1 and its guide said @v1, but
the workflow and its scripts exist only from v2.1.0. The default of the
five reusable workflows is now the current major, defined once in
MAJOR_TAG, and tests/test_tools_ref.py fails when a default differs from
it or names a tag without the script. Guides, README and wiki (en, da,
ms) call code-metrics.yml at @v2; ADR-0005, 0008, 0009 and 0010 carry
an amendment; RC-077 accepts the milestone's task 1 results.

Task: MIL-011#2

guides/quality-checks-cpp.md

@@ -31,7 +31,7 @@ jobs:
 | `compile-commands-dir` | empty | Directory, relative to the repository root, with a `compile_commands.json` that your pipeline built before the call; when set, clang-tidy uses it and ignores `std` |
 | `clang-format-version` | `23.1.3` | Exact version of the clang-format package |
 | `clang-tidy-version` | `22.1.8` | Exact version of the clang-tidy package |
-| `tools-ref` | `v1` | Tag or branch of `TirSystem/github-action` from which the script `tools/quality-checks-cpp.sh` is fetched |
+| `tools-ref` | `v2` | Tag or branch of `TirSystem/github-action` from which the script `tools/quality-checks-cpp.sh` is fetched |
 
 Reference the workflow at the major tag (`@v1`) or at an exact tag, never at
 `main`. A call at an exact tag is pinned completely only when `tools-ref` names