feat: convert ssh tunnels into a plugin

plugins/tunnels/tests/backend/c2s-source-host.test.ts

@@ -0,0 +1,31 @@
+import { describe, expect, it, vi } from "vitest";
+import { resolveC2SSourceHostId } from "../../src/backend/c2s-relay.js";
+
+describe("resolveC2SSourceHostId", () => {
+  it("uses the row matching the stable sync id", async () => {
+    const findBySyncId = vi.fn().mockResolvedValue(42);
+
+    await expect(
+      resolveC2SSourceHostId(
+        { sourceHostId: 7, sourceHostSyncId: "host-sync-id" },
+        findBySyncId,
+      ),
+    ).resolves.toBe(42);
+    expect(findBySyncId).toHaveBeenCalledWith("host-sync-id");
+  });
+
+  it("keeps a local id when no sync id is available", async () => {
+    await expect(
+      resolveC2SSourceHostId({ sourceHostId: 7 }, vi.fn()),
+    ).resolves.toBe(7);
+  });
+
+  it("does not silently fall back to a mismatched id", async () => {
+    await expect(
+      resolveC2SSourceHostId(
+        { sourceHostId: 7, sourceHostSyncId: "missing" },
+        vi.fn().mockResolvedValue(null),
+      ),
+    ).rejects.toThrow("not found on the remote server");
+  });
+});