docs(schedules): explain archive-on-finish behavior

The schedule and worktree guides omitted the existing retention control and its default. Document the app setting and clarify that CLI and MCP tools do not expose it.

packages/website/src/schedule-docs.test.ts

@@ -0,0 +1,16 @@
+import { readFile } from "node:fs/promises";
+import path from "node:path";
+import { expect, it } from "vitest";
+
+const docsRoot = path.resolve(import.meta.dirname, "../../../public-docs");
+
+it.each(["schedules.md", "schedules-cli.md", "mcp.md", "worktrees.md"])(
+  "%s makes schedule run retention discoverable",
+  async (file) => {
+    const markdown = await readFile(path.join(docsRoot, file), "utf8");
+    expect(markdown).toContain("Archive on finish");
+    if (file !== "schedules.md") {
+      expect(markdown).toContain("/docs/schedules#keep-run-workspaces");
+    }
+  },
+);