Integrate ImpedenceFinder closed-form Z0 into the project Impedance tab.

Use the vendored Hammerstad-Jensen/Cohn engine for microstrip, stripline, and coupled-diff advice. Skip OpenEMS/pcbnew and refuse CPWG rather than inventing a number.

Co-authored-by: Cursor <cursoragent@cursor.com>

frontend/src/lib/api.ts

@@ -10,6 +10,9 @@ import type {
   CreditSnapshot,
   DesignGraph,
   DeratingRow,
+  ImpedanceKind,
+  ImpedanceStackupResult,
+  ImpedanceTraceResult,
   EdifSubDesign,
   FindingComment,
   LcscPayload,
@@ -582,6 +585,28 @@ export async function fetchDerating(
   return res.json();
 }
 
+export async function computeImpedance(body: {
+  mode: "trace" | "stackup";
+  kind?: ImpedanceKind;
+  h: number;
+  er: number;
+  t: number;
+  w?: number | null;
+  s?: number | null;
+  target_z?: number | null;
+}): Promise<ImpedanceTraceResult | ImpedanceStackupResult> {
+  const res = await authFetch(`${BASE}/api/impedance`, {
+    method: "POST",
+    headers: { "Content-Type": "application/json" },
+    body: JSON.stringify(body),
+  });
+  if (!res.ok) {
+    const detail = await res.json().catch(() => ({ detail: res.statusText }));
+    throw new Error(typeof detail.detail === "string" ? detail.detail : "Impedance compute failed");
+  }
+  return res.json();
+}
+
 export async function fetchReport(
   projectId: string,
 ): Promise<ValidationReport> {

frontend/src/lib/types.ts

@@ -320,6 +320,32 @@ export interface DeratingSettings {
   electrolytic: number;
 }
 
+export type ImpedanceKind = "microstrip" | "stripline" | "cpw" | "diff";
+
+export interface ImpedanceTraceResult {
+  kind: ImpedanceKind;
+  z0?: number | null;
+  zodd?: number | null;
+  zeven?: number | null;
+  zdiff?: number | null;
+  w_mm?: number | null;
+  s_mm?: number | null;
+}
+
+export interface ImpedanceTarget {
+  kind: string;
+  w_mm: number | null;
+  s_mm: number | null;
+  z0: number | null;
+  zdiff: number | null;
+  formula: string;
+}
+
+export interface ImpedanceStackupResult {
+  targets: Record<string, ImpedanceTarget>;
+  kicad_dru: string;
+}
+
 export interface NetlistPreviewDesignator {
   ref: string;
   pins: { number: string; net_name: string }[];