[rig-claude] Improve Claude dynamic-workflow compatibility for rig

skills/rig/samples/330-nested-workflow-composition.md

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+# 330 - Nested Workflow Composition (call.workflow)
+
+Demonstrates `call.workflow` — the rig equivalent of `workflow(ref, args)` in
+Claude dynamic workflows. A parent workflow delegates a self-contained child
+workflow inline. The child shares the parent's concurrency limiter, agent
+budget, cancellation signal, and event stream.
+
+See [claude-workflow-conversion.md](../references/claude-workflow-conversion.md)
+for the full primitive mapping and
+[dynamic-workflows.md](../references/dynamic-workflows.md) for `call.workflow`
+semantics.
+
+```rig
+import { s, workflow } from "rig";
+
+// Workflow role: scan one directory for issues and return structured findings.
+const scanDir = workflow({
+  meta: {
+    name: "scanDir",
+    description: "Scan a directory for issues",
+    phases: ["Scan"],
+  },
+  input: s.object({ dir: s.path }),
+  body: async ({ call, input, phase }) => {
+    phase("Scan");
+    return call.json(
+      `List up to 5 issues found in ${input.dir}. Be specific.`,
+      s.object({ issues: s.array(s.string) }),
+      { label: input.dir },
+    );
+  },
+});
+
+// Workflow role: run scanDir on each root area, then produce a combined report.
+// Mirrors Claude dynamic-workflow pattern: `await workflow(ref, args)` becomes
+// `await call.workflow(child, args)` — the child runs inline on the same budget.
+const fullAudit = workflow({
+  meta: {
+    name: "fullAudit",
+    description: "Audit several directories and produce a combined report",
+    phases: ["Audit", "Report"],
+  },
+  body: async ({ call, phase }) => {
+    phase("Audit");
+    const dirs = ["src", "skills", "scripts"];
+    const results = await Promise.all(
+      dirs.map((dir) => call.workflow(scanDir, { dir }, { label: dir })),
+    );
+
+    phase("Report");
+    const allIssues = results.flatMap((r, i) =>
+      (r?.issues ?? []).map((issue) => `[${dirs[i]}] ${issue}`),
+    );
+    return call.json(
+      `Summarise these issues into a short executive report:\n${allIssues.join("\n")}`,
+      s.object({ summary: s.string, severity: s.enum("low", "medium", "high") }),
+    );
+  },
+});
+
+export default fullAudit;
+```