feat: harden runtime readiness and session workflow

backend/test/readiness-manager.test.ts

@@ -0,0 +1,62 @@
+import { expect, test } from "vitest";
+import { ReadinessManager } from "../src/runtime/readiness-manager.js";
+
+function deferred<T>() {
+  let resolve!: (value: T) => void;
+  const promise = new Promise<T>((r) => { resolve = r; });
+  return { promise, resolve };
+}
+
+test("readiness is single-flight per workspace and caches a short-lived success", async () => {
+  let now = 1_000;
+  let calls = 0;
+  const first = deferred<any>();
+  const tht = {
+    ollamaEnsure: async () => {
+      calls += 1;
+      return first.promise;
+    },
+  } as any;
+  const readiness = new ReadinessManager(tht, 60, 500, () => now);
+
+  const a = readiness.ensure("psd");
+  const b = readiness.ensure("psd");
+  expect(calls).toBe(1);
+  first.resolve({ ok: true, model_name: "embed" });
+  await expect(a).resolves.toMatchObject({ ok: true });
+  await expect(b).resolves.toMatchObject({ ok: true });
+
+  await readiness.ensure("psd");
+  expect(calls).toBe(1);
+  now += 501;
+  tht.ollamaEnsure = async () => { calls += 1; return { ok: true }; };
+  await readiness.ensure("psd");
+  expect(calls).toBe(2);
+});
+
+test("readiness keys workspaces independently", async () => {
+  const seen: string[] = [];
+  const tht = {
+    ollamaEnsure: async (workspace: string) => {
+      seen.push(workspace);
+      return { ok: true };
+    },
+  } as any;
+  const readiness = new ReadinessManager(tht, 60);
+  await Promise.all([readiness.ensure("a"), readiness.ensure("b")]);
+  expect(seen.sort()).toEqual(["a", "b"]);
+});
+
+test("readiness does not cache failed results", async () => {
+  let calls = 0;
+  const tht = {
+    ollamaEnsure: async () => {
+      calls += 1;
+      return calls === 1 ? { ok: false, error: "down" } : { ok: true };
+    },
+  } as any;
+  const readiness = new ReadinessManager(tht, 60);
+  await expect(readiness.ensure("psd")).resolves.toMatchObject({ ok: false });
+  await expect(readiness.ensure("psd")).resolves.toMatchObject({ ok: true });
+  expect(calls).toBe(2);
+});