Native overlay of graph, parsers, models, taxonomy; Periscope mark.

Src-first imports now load graph/parsers/EDIF/models/taxonomy from
periscope/src. Inherited copies stay in dependency/. Taxonomy JSON path
uses repo_paths. New periscope/lens mark at existing 16/32/180/192/512
favicon sizes; header uses PeriscopeMark instead of the lucide CPU glyph.

tests/test_native_graph_overlay.py

@@ -0,0 +1,36 @@
+"""Native overlay: graph, parsers, models, taxonomy resolve from periscope/src."""
+
+from __future__ import annotations
+
+from pathlib import Path
+
+import backend.periscopex.graph as graph
+import backend.periscopex.models as models
+import backend.periscopex.parsers as parsers
+import backend.periscopex.parsers_edif as parsers_edif
+import backend.periscopex.taxonomy as taxonomy
+
+
+def _src_file(mod) -> Path:
+    return Path(mod.__file__).resolve()
+
+
+def test_graph_parsers_models_taxonomy_load_from_src():
+    root = Path(__file__).resolve().parents[1]
+    src = (root / "periscope" / "src" / "backend" / "periscopex").resolve()
+    for mod, name in (
+        (graph, "graph.py"),
+        (models, "models.py"),
+        (parsers, "parsers.py"),
+        (parsers_edif, "parsers_edif.py"),
+        (taxonomy, "taxonomy.py"),
+    ):
+        path = _src_file(mod)
+        assert path == src / name, path
+        assert "Native Periscope overlay" in path.read_text(encoding="utf-8")[:400]
+
+
+def test_taxonomy_dir_points_at_inherited_json():
+    ic = taxonomy.TAXONOMY_DIR / "ic.json"
+    assert ic.is_file(), taxonomy.TAXONOMY_DIR
+    assert "src/taxonomy" not in str(taxonomy.TAXONOMY_DIR)