i18n(core): route order-coordinator and token/margin guards through t()

These files bypassed the i18n table entirely, so a user running LANG=en still
got Chinese order logs. Migrating them surfaced structural duplication too: the
five order paths each spelled out their own 'quantity invalid' string, now one
key parameterised by an order-kind label.

Also fixes a type that carried display text as its domain: TrendLabel was
'做多' | '做空' | '无信号', so the engine's snapshot value *was* the Chinese
string and English rendering depended on matching it. Now 'long' | 'short' |
'none', translated at the edge.

Order-coordinator tests asserted the Chinese literals, which is exactly what
made the gap invisible; they now assert the resolved key so they hold in either
language.

39 new translation keys. 271 pass; tsc and oxlint clean.

src/strategy/trend-engine.ts

@@ -32,6 +32,7 @@ import { createTradeLog, type TradeLogEntry } from "../logging/trade-log";
 import { decryptCopyright } from "../utils/copyright";
 import { isRateLimitError } from "../utils/errors";
 import { RateLimitController } from "../core/lib/rate-limit";
+import type { TrendLabel } from "../utils/format";
 import { StrategyEventEmitter } from "./common/event-emitter";
 import { createPrecisionSyncer, type PrecisionSyncer } from "./common/precision-syncer";
 import { safeSubscribe, type LogHandler } from "./common/subscriptions";
@@ -44,7 +45,7 @@ export interface TrendEngineSnapshot {
   lastPrice: number | null;
   sma30: number | null;
   bollingerBandwidth: number | null;
-  trend: "做多" | "做空" | "无信号";
+  trend: TrendLabel;
   position: PositionSnapshot;
   pnl: number;
   unrealized: number;
@@ -978,13 +979,14 @@ export class TrendEngine {
     const position = getPosition(this.accountSnapshot, this.config.symbol);
     const price = this.tickerSnapshot ? Number(this.tickerSnapshot.lastPrice) : null;
     const sma30 = this.lastSma30;
-    const trend = price == null || sma30 == null
-      ? "无信号"
-      : price > sma30
-      ? "做多"
-      : price < sma30
-      ? "做空"
-      : "无信号";
+    const trend: TrendLabel =
+      price == null || sma30 == null
+        ? "none"
+        : price > sma30
+          ? "long"
+          : price < sma30
+            ? "short"
+            : "none";
     const pnl = price != null ? computePositionPnl(position, price, price) : 0;
     return {
       ready: this.isReady(),