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

README.md

@@ -240,7 +240,7 @@ deactivate Workflow
 
 ### 🏅 Code metrics
 
-A reusable workflow that counts the code files and the lines of code (without comment and blank lines) of a repository and publishes them, with the test coverage, as three SVG badges on a `badges` branch, called with `uses: TirSystem/github-action/.gitea/workflows/code-metrics.yml@v1` (ADR-0010). It needs `contents: write` and runs no test: an earlier job of the caller produces a Cobertura XML coverage report and uploads it as an artifact ([guide](guides/code-metrics.md)).
+A reusable workflow that counts the code files and the lines of code (without comment and blank lines) of a repository and publishes them, with the test coverage, as three SVG badges on a `badges` branch, called with `uses: TirSystem/github-action/.gitea/workflows/code-metrics.yml@v2` (ADR-0010). It needs `contents: write` and runs no test: an earlier job of the caller produces a Cobertura XML coverage report and uploads it as an artifact ([guide](guides/code-metrics.md)).
 
 #### 🔀 Workflow
 
@@ -250,7 +250,7 @@ title Code metrics and coverage badges (reusable workflow)
 
 autonumber
 
-actor "Calling repository\nuses: ...code-metrics.yml@v1" as Caller
+actor "Calling repository\nuses: ...code-metrics.yml@v2" as Caller
 participant "Gitea Actions\ncode-metrics" as Workflow
 participant "Branch badges\nof the caller" as Branch