relations: weakly-connected components (component, components partition, count) + 11 tests

tree.sx, reuses ureach-bfs. 158/158 across 9 suites.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

lib/relations/conformance.conf

@@ -31,4 +31,5 @@ SUITES=(
   "tree:lib/relations/tests/tree.sx:(relations-tree-tests-run!)"
   "routes:lib/relations/tests/routes.sx:(relations-routes-tests-run!)"
   "bulk:lib/relations/tests/bulk.sx:(relations-bulk-tests-run!)"
+  "comp:lib/relations/tests/comp.sx:(relations-comp-tests-run!)"
 )