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least-squares fit over all five points — not merely out of date but the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

src/nodes/face_aligner_node.hpp

@@ -4,12 +4,16 @@
 #include <iostream>
 
 // ── FaceAlignerFunc ───────────────────────────────────────────────────────────
+/// TRACES: AR-005, AR-030 | SR-002
+///
 // KPN node: applies a 5-point similarity transform to each detected face,
 // producing a 112×112 BGR crop suitable for ArcFace inference.
 //
-// Alignment uses cv::estimateAffinePartial2D (RANSAC) to fit the detected
-// landmarks to ArcFace canonical positions.  Degenerate detections (where the
-// affine fit fails) are silently dropped from the output vectors.
+// Alignment is an Umeyama least-squares fit over all five landmarks (AR-005),
+// not a robust one: a RANSAC fit discards the very landmarks AR-030 reads.
+// Degenerate detections (where the fit fails) are dropped from the output
+// vectors. The fit's residual is the AR-030 visibility measure and comes free,
+// since the warp needs the transform anyway.
 
 struct FaceAlignerFunc {
     static constexpr std::string_view label() { return "face_aligner"; }