test: tag the untagged suites; correct two stale headers

Four test files and one node header carried no TRACES tag, so the
requirements they verify read as implemented-but-unverified. Tagging a
test is what distinguishes the two.

test_calibration.cpp is AR-023; its three [report] cases verify GR-003
and are tagged separately, since the report is fitted from the same
distributions but is its own requirement. test_similarity.cpp is the CI
half of AR-026 — equivalence against hand-computed dot products, where
throughput at scale is AR-027 and cannot run on this host.
test_face_tracker.cpp is AR-007 and AR-008.

Two headers described code that no longer exists. face_aligner_node.hpp
still documented the RANSAC fit AR-005 replaced with an Umeyama
least-squares fit over all five points — not merely out of date but the
opposite of what the file does, and it reads as a rationale for
discarding the landmarks AR-030 measures. test_face_tracker.cpp still
described the park/revive branch AR-008 deleted, and the raw-cosine
cut_revive_sim that guarded it, which AR-024 retired.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

TRACES: AR-005, AR-007, AR-008, AR-023, AR-026, AR-030 | GR-003 | SR-001, SR-002

tests/test_similarity.cpp

@@ -1,5 +1,11 @@
+// TRACES: AR-026 | SR-001
+//
 // Unit tests for the CPU reference similarity engine (backends/gemm_backend.cpp,
 // SAE_GEMM_CPU) and the l2_normalise helper. All pure, GPU-free, model-free.
+//
+// This is the CI half of AR-026: equivalence between the GEMM path and
+// hand-computed dot products on small input. Throughput at scale (AR-027) is T4
+// and cannot run here.
 #include <catch2/catch_test_macros.hpp>
 #include <catch2/matchers/catch_matchers_floating_point.hpp>