Split native Periscope (periscope/src) from inherited PinScope (periscope/dependency).

Keep validate.py and the finding engine as-is. AGPL LICENSE stays at the repo root.
Docker overlays dependency then src. Do not delete the inherited tree.

tests/test_crystal_cl_check.py

@@ -2,6 +2,8 @@
 
 from __future__ import annotations
 
+from tests.paths import SIMPLE_PROJECT, TAXONOMY
+
 from backend.periscopex.crystal_cl_check import check_crystal_cl
 from backend.periscopex.models import (
     Component,
@@ -92,6 +94,6 @@ def test_with_stray_mismatch_warns():
 def test_simple_project_without_cl_silent():
     from pathlib import Path
     from backend.periscopex.models import DesignGraph
-    path = Path(__file__).resolve().parents[1] / "simple_project" / "design_graph.json"
+    path = SIMPLE_PROJECT / "design_graph.json"
     g = DesignGraph.model_validate_json(path.read_text())
     assert check_crystal_cl(g) == []