chore: exclude generated fixtures and lockfiles via gitattributes

Mark recorded test-resource dumps (dependencies-outputs/, projects-outputs/),
ApprovalTests snapshots (*.approved.txt), and package manager lockfiles as
generated so they are excluded from code-size analyses.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Author: ragunathjawahar

.gitattributes

@@ -0,0 +1,12 @@
+# Recorded test-resource fixtures: generated dumps of real-project build output
+# (e.g. gradle dependency / project-structure listings), not hand-written code.
+build-systems/gradle/src/test/resources/dependencies-outputs/** linguist-generated
+build-systems/gradle/src/test/resources/projects-outputs/** linguist-generated
+
+# ApprovalTests-generated snapshot files.
+**/*.approved.txt linguist-generated
+
+# Dependency lockfiles (generated by package managers).
+**/package-lock.json linguist-generated
+**/yarn.lock linguist-generated
+**/pnpm-lock.yaml linguist-generated