FN-5986: add browser demo lifecycle board flow

Add a browser demo workflow and supporting fixtures for board walkthroughs.

- add a demo README plus seeded Browser Demo Lifecycle workflow with Todo, In Progress, In Review, QA, and Publish columns
- seed representative browser demo tasks and lifecycle log entries across the custom workflow columns
- update the live simulator to advance workflow tasks through QA and Publish while preserving the legacy merge path
- add a core lifecycle test covering workflow selection and the Todo → In Progress → In Review → QA → Publish transitions

Files changed:
 demo/README.md                                     |  25 ++++
 demo/seed.ts                                       | 131 ++++++++++++++++++++-
 demo/simulate.ts                                   |  35 ++++--
 packages/core/src/__tests__/browser-demo-lifecycle.test.ts   |  71 +++++++++++
 4 files changed, 248 insertions(+), 14 deletions(-)

Fusion-Task-Id: FN-5986

Fusion-Task-Lineage: 9638f7da-9b50-4de1-8ffa-d861dbf7aff2

packages/core/src/__tests__/browser-demo-lifecycle.test.ts

@@ -0,0 +1,71 @@
+// @vitest-environment node
+
+import { describe, it, expect, beforeEach, afterEach } from "vitest";
+
+import type { WorkflowIr } from "../workflow-ir-types.js";
+import { createTaskStoreTestHarness } from "./store-test-helpers.js";
+
+function browserDemoLifecycleIr(): WorkflowIr {
+  return {
+    version: "v2",
+    name: "browser-demo-lifecycle",
+    columns: [
+      { id: "todo", name: "Todo", traits: [{ trait: "intake" }] },
+      { id: "in-progress", name: "In Progress", traits: [{ trait: "wip" }] },
+      { id: "in-review", name: "In Review", traits: [{ trait: "merge-blocker" }] },
+      { id: "qa", name: "QA", traits: [] },
+      { id: "publish", name: "Publish", traits: [{ trait: "complete" }] },
+    ],
+    nodes: [
+      { id: "start", kind: "start", column: "todo" },
+      { id: "implement", kind: "prompt", column: "in-progress", config: { prompt: "Implement" } },
+      { id: "review", kind: "prompt", column: "in-review", config: { prompt: "Review" } },
+      { id: "qa-check", kind: "gate", column: "qa", config: { scriptName: "test", name: "QA" } },
+      { id: "end", kind: "end", column: "publish" },
+    ],
+    edges: [
+      { from: "start", to: "implement", condition: "success" },
+      { from: "implement", to: "review", condition: "success" },
+      { from: "review", to: "qa-check", condition: "success" },
+      { from: "qa-check", to: "end", condition: "success" },
+    ],
+  };
+}
+
+describe("browser demo lifecycle workflow", () => {
+  const harness = createTaskStoreTestHarness();
+  let store: ReturnType<typeof harness.store>;
+
+  beforeEach(async () => {
+    await harness.beforeEach();
+    store = harness.store();
+    await store.updateGlobalSettings({ experimentalFeatures: { workflowColumns: true } });
+  });
+
+  afterEach(async () => {
+    await harness.afterEach();
+  });
+
+  it("supports the Todo → In Progress → In Review → QA → Publish board walkthrough", async () => {
+    const workflow = await store.createWorkflowDefinition({
+      name: "Browser Demo Lifecycle",
+      ir: browserDemoLifecycleIr(),
+    });
+    const task = await store.createTask({ description: "Browser walkthrough task", title: "Demo lifecycle" });
+
+    const selection = await store.selectTaskWorkflowAndReconcile(task.id, workflow.id);
+    expect(selection.reconciliation).toEqual({ preserved: false, fromColumn: "triage", toColumn: "todo" });
+    expect((await store.getTask(task.id)).column).toBe("todo");
+
+    await store.moveTask(task.id, "in-progress", { moveSource: "user" });
+    await store.moveTask(task.id, "in-review", { moveSource: "user", allowDirectInReviewMove: true });
+    await store.moveTask(task.id, "qa", { moveSource: "user" });
+    await store.moveTask(task.id, "publish", { moveSource: "user" });
+
+    const detail = await store.getTask(task.id);
+    expect(detail.column).toBe("publish");
+
+    const listed = await store.listTasks({ column: "publish" });
+    expect(listed.map((item) => item.id)).toContain(task.id);
+  });
+});