feat(selection): show stock industry and concept boards in detail panel

Add point-in-time stock membership lookup to the sector radar module
(GET /sector-radar/stocks/{ts_code}/membership) reading the existing
dc_index/dc_member snapshots, and surface industries plus concept chips
in the selection signal detail panel with graceful no-data hiding.

zhixing-web/src/features/sector-radar/api/sector-radar.api.ts

@@ -14,6 +14,8 @@ import {
   type RadarRankingRow,
   type RadarRankingsQuery,
   type RadarRankingsResponse,
+  type StockSectorMembershipResponse,
+  type StockSectorRef,
 } from "./sector-radar.types"
 
 type JsonRecord = Record<string, unknown>
@@ -145,6 +147,69 @@ export function parseRadarRankingsResponse(
   }
 }
 
+/**
+ * Fetch one stock's industries and concepts from the last-good build snapshot.
+ *
+ * @param tsCode - Stock code such as `000001.SZ`.
+ * @param tradeDate - Requested trade date; the backend answers with the
+ *   newest snapshot at or before it and reports that exact date.
+ * @param signal - React Query cancellation signal forwarded to fetch.
+ * @returns A validated membership response with grouped sector references.
+ * @throws Error when the server response violates the stable HTTP contract.
+ */
+export async function getStockSectorMembership(
+  tsCode: string,
+  tradeDate: string,
+  signal?: AbortSignal,
+) {
+  const params = new URLSearchParams({ trade_date: tradeDate })
+  const payload = await requestJson<unknown>(
+    `/api/v1/sector-radar/stocks/${encodeURIComponent(tsCode)}/membership?${params.toString()}`,
+    { signal },
+  )
+  return parseStockSectorMembershipResponse(payload)
+}
+
+/** Validate one stock-membership response at the feature boundary. */
+export function parseStockSectorMembershipResponse(
+  value: unknown,
+): StockSectorMembershipResponse {
+  const record = readRecord(value, "membership")
+  return {
+    status: readEnum(record.status, ["success", "no_data"], "membership.status"),
+    ts_code: readNonEmptyString(record.ts_code, "membership.ts_code"),
+    requested_trade_date: readDate(
+      record.requested_trade_date,
+      "membership.requested_trade_date",
+    ),
+    trade_date: readNullableDate(record.trade_date, "membership.trade_date"),
+    industries: readSectorRefs(record.industries, "membership.industries"),
+    concepts: readSectorRefs(record.concepts, "membership.concepts"),
+    concept_total: readIntegerInRange(
+      record.concept_total,
+      0,
+      Number.MAX_SAFE_INTEGER,
+      "membership.concept_total",
+    ),
+    concept_limit: readIntegerInRange(
+      record.concept_limit,
+      1,
+      100,
+      "membership.concept_limit",
+    ),
+  }
+}
+
+function readSectorRefs(value: unknown, path: string): StockSectorRef[] {
+  return readArray(value, path).map((item, index) => {
+    const ref = readRecord(item, `${path}[${index}]`)
+    return {
+      code: readNonEmptyString(ref.code, `${path}[${index}].code`),
+      name: readNonEmptyString(ref.name, `${path}[${index}].name`),
+    }
+  })
+}
+
 function readNullablePublication(
   value: unknown,
   path: string,