feat: add Signal provider support

src/signal/probe.ts

@@ -0,0 +1,47 @@
+import { signalCheck, signalRpcRequest } from "./client.js";
+
+export type SignalProbe = {
+  ok: boolean;
+  status?: number | null;
+  error?: string | null;
+  elapsedMs: number;
+  version?: string | null;
+};
+
+export async function probeSignal(
+  baseUrl: string,
+  timeoutMs: number,
+): Promise<SignalProbe> {
+  const started = Date.now();
+  const result: SignalProbe = {
+    ok: false,
+    status: null,
+    error: null,
+    elapsedMs: 0,
+    version: null,
+  };
+  const check = await signalCheck(baseUrl, timeoutMs);
+  if (!check.ok) {
+    return {
+      ...result,
+      status: check.status ?? null,
+      error: check.error ?? "unreachable",
+      elapsedMs: Date.now() - started,
+    };
+  }
+  try {
+    const version = await signalRpcRequest<string>("version", undefined, {
+      baseUrl,
+      timeoutMs,
+    });
+    result.version = typeof version === "string" ? version : null;
+  } catch (err) {
+    result.error = err instanceof Error ? err.message : String(err);
+  }
+  return {
+    ...result,
+    ok: true,
+    status: check.status ?? null,
+    elapsedMs: Date.now() - started,
+  };
+}