Fix core/doc Scaladoc failure from a broken ProjectRef doc-link (#146)

[teeckoo (teeckoo)]

Follow-up to #147 (which fixed #146). After the merge, master CI went red — this PR greens it.

What's broken

core / Compile / doc fails:

SbtProjectStructureExtractorBase.scala:19:3: Could not find any member to link for "ProjectRef".
one error found
(core / Compile / doc) Scaladoc generation failed

A review-fix doc comment on projectMap referenced sbt.ProjectRef via a [[ProjectRef]] doc-link. ProjectRef is an external library type with no Scaladoc
apiMapping on the doc classpath, so the link can't be resolved, and the build fails doc on broken links.

Why CI shows it as test failures too

It's a single root cause. The integration-test setup runs compile ; publishLocal ; show core / version; publishLocal invokes doc, so the child sbt process
exits 1 and every publishCurrentSbtIdeaPluginToLocalRepoAndGetVersions-based test fails (Simple project with plugin, provided module names cache ..., etc.). No
separate test regression.

---

Fix

Swap the doc-link for a plain code span — renders the same, resolves nothing:

- * Maps each [[ProjectRef]] of the current build to its extracted project data.
+ * Maps each `ProjectRef` of the current build to its extracted project data.

Verification

Locally on this branch (off current master):

• core/doc, packaging/doc, ideaSupport/doc → all generate successfully (3/3), zero errors
• the publishLocal path the integration tests use no longer fails

The other doc-links added in #147 ([[projectMap]], [[processLibraries]], [[buildExternalProjectData]], [[SbtPackageProjectData]]) all point to in-project
members and resolve fine — [[ProjectRef]] was the only break.