Rewrite leftover analysis modules imported by src.

validate/validation_tools alias native lookup and review tools. Passive
resolve, derating, BOM summary, pin-mux, LED current, and net-function
tokens are original Periscope code. finding_engine and pcb_* unchanged.

tests/test_periscope_analysis_rewrite.py

@@ -0,0 +1,21 @@
+"""Prove leftover analysis modules live in periscope/src."""
+
+from __future__ import annotations
+
+from pathlib import Path
+
+
+def test_analysis_leftovers_are_src():
+    import backend.periscopex.validate as v
+    import backend.periscopex.validation_tools as vt
+    import backend.periscopex.resolve_passives as rp
+    import backend.periscopex.derating as d
+    import backend.periscopex.bom_summary as bs
+    import backend.periscopex.pin_mux_check as mux
+    import backend.periscopex.led_current_check as led
+    import backend.periscopex.pin_function_tokens as tok
+
+    for mod in (v, vt, rp, d, bs, mux, led, tok):
+        parts = Path(mod.__file__).resolve().parts
+        assert "src" in parts
+        assert "dependency" not in parts[-6:]