Mention plain mvn and add a PowerShell implementer search

skills/kotlin-tooling-immutable-collections-0-5-x-migration/SKILL.md

@@ -40,7 +40,8 @@ Check the version the project currently uses:
 ### 1. Find the build command
 
 Check `README.md`, `CLAUDE.md`, or `AGENTS.md` for how the project builds; if it isn't
-written down, infer it from the build files — Gradle (`./gradlew`), Maven (`./mvnw`), Bazel
+written down, infer it from the build files — Gradle (`./gradlew`), Maven (`mvn`, or the
+`./mvnw` wrapper), Bazel
 (a `bazel` wrapper), or a custom script. Record the compile command (and the test command).
 In a multi-module project you only need the modules that use the library, plus any you
 change — not a whole-repo build.
@@ -116,6 +117,13 @@ grep -rnE --include='*.kt' \
   '(class|object|interface)\s+\w[^:]*:\s*[^{]*\b(PersistentList|PersistentMap|PersistentSet|PersistentCollection)\s*<' .
 ```
 
+On Windows PowerShell, `Select-String` is the `grep` equivalent:
+
+```powershell
+Get-ChildItem -Recurse -Filter *.kt |
+  Select-String '(class|object|interface)\s+\w[^:]*:\s*[^{]*\b(PersistentList|PersistentMap|PersistentSet|PersistentCollection)\s*<'
+```
+
 (Confirm a match really lists the interface as a *supertype*, not just a field type or type
 argument.) For each, move the implementation into the new participial method and have the
 deprecated override delegate to it: