feat(gpr): explicitly mark GlobalPlaceRecognition as AnyLoc-VLAD-DINOv2 baseline

GlobalPlaceRecognition already implements AnyLoc-VLAD-DINOv2 (existing code).
This change makes the sprint 1 GPR technology selection explicit:

- Expand class docstring with selection rationale vs NetVLAD / SP+LG
- Document INT8 quantization as known-broken for ViT on Jetson
- Reference design doc §2.3 and stage2 backlog
- Add two marker tests asserting 4096-d descriptor + DINOv2 engine name

No behavioral change — existing Mock/TRT path unchanged.
Ref: docs/superpowers/specs/2026-04-18-oss-stack-tech-audit-design.md §2.3

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/gps_denied/core/gpr.py

@@ -62,12 +62,21 @@ class IGlobalPlaceRecognition(ABC):
 
 
 class GlobalPlaceRecognition(IGlobalPlaceRecognition):
-    """AnyLoc (DINOv2) coarse localisation component.
+    """AnyLoc-VLAD-DINOv2 coarse localisation component — sprint 1 GPR baseline.
 
     GPR-01: load_index() tries to open a real Faiss .index file; falls back to
             a NumPy L2 mock when the file is missing or Faiss is not installed.
-    GPR-02: Descriptor computed via DINOv2 engine (TRT on Jetson, Mock on dev/CI).
+    GPR-02: Descriptor computed via DINOv2 engine (TRT FP16 on Jetson, Mock on
+            dev/CI). INT8 quantization is disabled — broken for ViT on Jetson
+            (NVIDIA/TRT#4348, facebookresearch/dinov2#489).
     GPR-03: Candidates ranked by descriptor similarity (L2 → converted to [0,1]).
+
+    Selected over NetVLAD (deprecated, −2.4% R@1 on MSLS 2024) and SuperPoint+
+    LightGlue (unvalidated for cross-view UAV↔satellite gap at sprint 1).
+    Stage 2 evaluation: SP+LG+FAISS per _docs/03_backlog/stage2_ideas/.
+    Long-term target: EigenPlaces (ICCV 2023) — cleaner ONNX export.
+
+    Ref: docs/superpowers/specs/2026-04-18-oss-stack-tech-audit-design.md §2.3
     """
 
     _DIM = 4096  # DINOv2 VLAD descriptor dimension

tests/test_gpr.py

@@ -110,3 +110,36 @@ def test_descriptor_is_l2_normalised(gpr):
     img = np.random.randint(0, 255, (200, 200, 3), dtype=np.uint8)
     desc = gpr.compute_location_descriptor(img)
     assert np.isclose(np.linalg.norm(desc), 1.0, atol=1e-5)
+
+
+# ---------------------------------------------------------------------------
+# AnyLoc baseline markers — document sprint 1 GPR technology selection.
+# GlobalPlaceRecognition IS the AnyLoc-VLAD-DINOv2 baseline (see class docstring).
+# Ref: docs/superpowers/specs/2026-04-18-oss-stack-tech-audit-design.md §2.3
+# ---------------------------------------------------------------------------
+
+
+def test_anyloc_baseline_descriptor_dim_is_4096(gpr):
+    """AnyLoc-VLAD-DINOv2 baseline produces 4096-d descriptors (ViT-base + VLAD)."""
+    img = np.random.randint(0, 255, (224, 224, 3), dtype=np.uint8)
+    desc = gpr.compute_location_descriptor(img)
+    assert desc.shape == (4096,), (
+        f"AnyLoc-VLAD-DINOv2 expects 4096-d descriptor, got {desc.shape}. "
+        "If you changed this, update the baseline reference in "
+        "docs/superpowers/specs/2026-04-18-oss-stack-tech-audit-design.md §2.3"
+    )
+
+
+def test_anyloc_baseline_uses_dinov2_engine():
+    """Sprint 1 GPR baseline must call DINOv2 via ModelManager."""
+    from unittest.mock import MagicMock
+
+    from gps_denied.core.gpr import GlobalPlaceRecognition
+
+    mm = MagicMock()
+    mm.get_inference_engine.return_value.infer.return_value = np.ones(4096, dtype=np.float32)
+    gpr_local = GlobalPlaceRecognition(mm)
+    gpr_local.compute_location_descriptor(np.zeros((224, 224, 3), dtype=np.uint8))
+
+    # AnyLoc == DINOv2 + VLAD. Engine name must be "DINOv2".
+    mm.get_inference_engine.assert_called_with("DINOv2")