Keep the plugin ICD docs and jenkins-ci-rme/README.md

Revert part of the markdown cleanup: the two TrainingAreaBase plugin
ICD docs and jenkins-ci-rme/README.md stay in the tree; the root
migration/validation reports remain removed. README.md pointers to
jenkins-ci-rme/README.md are restored.

qt6-after/qt6-migrated-legatus/README.md

@@ -38,7 +38,7 @@ The group target lists are the `GROUP*_TARGETS` arrays in
 - `new_docker_build_release2.sh` — Release 2 build driver (compile, ctest, DEB packaging, coverage)
 - `Dockerfile` — recipe of the build image (Ubuntu 26.04 + Qt 6.10.2 + deps)
 - `rpmbuild/make_rpm_ubuntu26_release2.py` — Release 2 DEB package producer (5 packages)
-- `jenkins-ci-rme/` — in-tree copy of the Jenkins CI flow (Jenkinsfile, builder, publisher, local dry run)
+- `jenkins-ci-rme/` — in-tree copy of the Jenkins CI flow (see its own `README.md`)
 - `build4_<timestamp>_<pid>/` — per-run build tree, created by the driver (git-ignored via `build4_*`)
 
 **Toolchain inside the image:** Ubuntu 26.04, Qt 6.10.2 (`/opt/Qt/6.10.2/gcc_64`),
@@ -231,12 +231,7 @@ local dry run of the same flow without Jenkins:
 jenkins-ci-rme/release-16-10-2026.sh
 ```
 
-The pipeline files: `jenkins-ci-rme/Jenkinsfile` (job entry point),
-`jenkins-ci-rme/jenkins/Jenkinsfile` (build body: install the prebuilt
-image when missing, run the builder, coverage, publish),
-`jenkins-ci-rme/jenkins_builder_ubuntu26.sh` (in-container DEB build),
-`jenkins-ci-rme/jenkins_publisher_ubuntu26.sh` (upload to the artifact
-repository).
+See `jenkins-ci-rme/README.md` for the pipeline details.
 
 ## Step 5 — Code coverage (lcov)