fix(uptime): сбросить снимок при смене пары и сохранить историю

lib/speed-probe-snapshot.test.ts

@@ -0,0 +1,27 @@
+import { test } from "node:test"
+import assert from "node:assert/strict"
+import { emptySpeedProbeObservations } from "@mmapp/contracts"
+import { publishSpeedProbeSnapshots } from "./speed-probe-snapshot"
+const probe = { id: "p", srcServerId: "1", dstServerId: "2", enabled: true, ...emptySpeedProbeObservations, lastTxAvgMbps: 0 as number | null, lastRxAvgMbps: 80 as number | null, lastStatus: "done" as "done" | "error" | null, lastRunAt: "2026-10-07T00:00:00Z" as string | null }
+test("same pair preserves latest zero and snapshot instead of readonly values copied into a stale draft", () => {
+  const next = { ...probe, enabled: false, lastTxAvgMbps: 999, lastRxAvgMbps: 999 }
+  const [saved] = publishSpeedProbeSnapshots([probe], [next])
+  assert.equal(saved.enabled, false)
+  assert.equal(saved.lastTxAvgMbps, 0)
+  assert.equal(saved.lastRxAvgMbps, 80)
+  assert.equal(saved.lastStatus, "done")
+  assert.equal(next.lastTxAvgMbps, 999)
+})
+for (const field of ["srcServerId", "dstServerId", "id"] as const) test(`changed ${field} starts with unknown measurements`, () => {
+  const [saved] = publishSpeedProbeSnapshots([probe], [{ ...probe, [field]: "3" }])
+  for (const key of Object.keys(emptySpeedProbeObservations)) assert.equal(saved[key as keyof typeof emptySpeedProbeObservations], null)
+  assert.equal(probe.lastRxAvgMbps, 80)
+})
+test("new row and reordered existing rows retain correct ownership without mutation", () => {
+  const next = { ...probe, id: "new" }
+  const saved = publishSpeedProbeSnapshots([probe], [next, probe])
+  assert.equal(saved[0].lastStatus, null)
+  assert.equal(saved[1].lastTxAvgMbps, 0)
+  assert.deepEqual(saved.map(p => p.id), ["new", "p"])
+  assert.equal(next.lastRxAvgMbps, 80)
+})