Bazel/Go: add some comments

go/extractor/BUILD.bazel

@@ -25,7 +25,9 @@ go_library(
     ],
 )
 
-# the other targets are not generated
+# the other targets are not generated by gazelle
+
+# this is separate from `tokenizer-jar` below because we don't want these compiled class files in the pack
 java_library(
     name = "tokenizer-deps",
     srcs = [
@@ -36,6 +38,7 @@ java_library(
     ],
 )
 
+# we only need these compiled class files in the pack
 java_library(
     name = "tokenizer-jar",
     srcs = [
@@ -51,7 +54,7 @@ pkg_files(
     srcs = [":tokenizer-jar"],
     prefix = "tools",
     renames = {
-        ":tokenizer-jar": "tokenizer.jar",
+        ":tokenizer-jar": "tokenizer.jar",  # name is `libtokenizer.jar` by default
     },
     visibility = ["//go:__pkg__"],
 )