Gate SI layout_rules to the quoted bus, not EN RC onto USB.

PE-SI-009 no longer treats ESP32 CHIP_PU/EN RC as a USB series R.
USB without a library Z number stays PE-SI-010 measurement-only.
Pintable skill 1.13.0 requires net_class on SI kinds (usb2/usb3/MDI/RGMII/DDR3).

backend/services/extraction.py

@@ -144,7 +144,9 @@ PINTABLE_TOOL = {
                     "number — never invent 3 mm/JEDEC), same_layer (bool), min_via_count, "
                     "max_via_count, z0_ohm, zdiff_ohm, tolerance_pct, z_min_ohm, z_max_ohm, "
                     "topology, min_spacing_mm, value_ohms, ref_plane, parameter, "
-                    "net_class, note, source_page. Empty array if the PDF has no layout guidance."
+                    "net_class (required for SI kinds: usb2 | usb3 | eth_mdi | rgmii | "
+                    "sgmii | ddr3 | hdmi | pcie | lvds — never map EN/CHIP_PU RC onto "
+                    "USB), note, source_page. Empty array if the PDF has no layout guidance."
                 ),
                 "items": {
                     "type": "object",