feat: add actor skill — frontmatter protocol + CAS reference

Adds 'uwf skill actor' command for agents executing workflow roles.
Covers the two things an actor needs to know:
1. Frontmatter output protocol (status field, schema-defined fields)
2. CAS operations (put, get, refs, walk, merkle DAG pattern)

Refs #540

packages/cli-workflow/src/__tests__/skill.test.ts

@@ -6,6 +6,7 @@ import { describe, expect, test } from "vitest";
 const __dirname = dirname(fileURLToPath(import.meta.url));
 
 import {
+  cmdSkillActor,
   cmdSkillArchitecture,
   cmdSkillCli,
   cmdSkillList,
@@ -21,8 +22,8 @@ describe("skill commands", () => {
     expect(result).toContain("architecture");
     expect(result).toContain("yaml");
     expect(result).toContain("moderator");
+    expect(result).toContain("actor");
     for (const name of result) {
-      expect(typeof name).toBe("string");
       expect(name).toMatch(/^\S+$/);
     }
   });
@@ -62,6 +63,15 @@ describe("skill commands", () => {
     expect(result).toContain("uwf");
   });
 
+  test("skill actor returns non-empty markdown string", () => {
+    const result = cmdSkillActor();
+    expect(typeof result).toBe("string");
+    expect(result).toContain("frontmatter");
+    expect(result).toContain("CAS");
+    expect(result).toContain("status");
+    expect(result.length).toBeGreaterThan(200);
+  });
+
   test("skill help subcommand is suppressed", () => {
     const output = execFileSync("bun", ["src/cli.ts", "skill", "--help"], {
       cwd: join(__dirname, "..", ".."),
@@ -73,6 +83,7 @@ describe("skill commands", () => {
     expect(output).toContain("architecture");
     expect(output).toContain("yaml");
     expect(output).toContain("moderator");
+    expect(output).toContain("actor");
     expect(output).toContain("list");
   });
 });

packages/cli-workflow/src/cli.ts

@@ -17,6 +17,7 @@ import { cmdConfigGet, cmdConfigList, cmdConfigSet } from "./commands/config.js"
 import { cmdLogClean, cmdLogList, cmdLogShow } from "./commands/log.js";
 import { cmdSetup, cmdSetupInteractive } from "./commands/setup.js";
 import {
+  cmdSkillActor,
   cmdSkillArchitecture,
   cmdSkillCli,
   cmdSkillList,
@@ -503,6 +504,13 @@ skill
     console.log(cmdSkillYaml());
   });
 
+skill
+  .command("actor")
+  .description("Print the actor reference (frontmatter protocol + CAS)")
+  .action(() => {
+    console.log(cmdSkillActor());
+  });
+
 skill
   .command("moderator")
   .description("Print the moderator reference")

packages/cli-workflow/src/commands/skill.ts

@@ -1,11 +1,12 @@
 export {
+  generateActorReference as cmdSkillActor,
   generateArchitectureReference as cmdSkillArchitecture,
   generateCliReference as cmdSkillCli,
   generateModeratorReference as cmdSkillModerator,
   generateYamlReference as cmdSkillYaml,
 } from "@uncaged/workflow-util";
 
-const SKILL_NAMES = ["cli", "architecture", "yaml", "moderator"] as const;
+const SKILL_NAMES = ["cli", "architecture", "yaml", "moderator", "actor"] as const;
 
 export function cmdSkillList(): ReadonlyArray<string> {
   return [...SKILL_NAMES];

packages/workflow-util/src/actor-reference.ts

@@ -0,0 +1,68 @@
+export function generateActorReference(): string {
+  return `# Actor Reference
+
+You are executing a workflow role. Your system prompt defines your goal, procedure, and output requirements. This reference covers two things you need to know about the workflow engine.
+
+## 1. Frontmatter Output Protocol
+
+Your response **MUST** begin with a YAML frontmatter block at byte position 0 — no preamble text before it.
+
+\`\`\`
+---
+status: done
+myField: some value
+---
+
+... markdown body (your work, explanation, notes) ...
+\`\`\`
+
+### Standard Field
+
+| Field | Values | Default | Description |
+|-------|--------|---------|-------------|
+| \`status\` | \`done\`, \`needs_input\`, \`in_progress\`, \`failed\` | \`done\` | Completion signal — determines which graph edge the moderator follows next |
+
+### Schema-Defined Fields
+
+Your role's output schema (shown in the system prompt under "Deliverable Format") defines additional fields. Output **only** the fields listed there — do not invent extra fields.
+
+### Body
+
+Everything after the closing \`---\` fence is the markdown body. Use it for explanations, logs, or human-readable notes. The body is stored but not parsed by the engine.
+
+### Retry
+
+If the engine cannot parse your frontmatter, it will ask you to retry (up to 2 times). Just output the corrected frontmatter block — don't panic.
+
+## 2. CAS (Content-Addressable Store)
+
+Your frontmatter output is automatically stored in CAS. You can also **use CAS directly** to store intermediate artifacts, build merkle DAGs for large outputs, or reference data from previous steps.
+
+### Commands
+
+\`\`\`
+uwf cas put-text <text>           # store plain text, print hash
+uwf cas put <type-hash> <json>    # store typed JSON data, print hash
+uwf cas get <hash>                # read a CAS node (type + payload)
+uwf cas has <hash>                # check if a hash exists
+uwf cas refs <hash>               # list direct references from a node
+uwf cas walk <hash>               # recursive traversal from a node
+uwf cas schema list               # list registered schemas
+uwf cas schema get <hash>         # show a schema definition
+\`\`\`
+
+### Merkle DAG Pattern
+
+For large outputs, store parts individually and reference their hashes:
+
+\`\`\`bash
+# Store individual sections
+HASH1=$(uwf cas put-text "section 1 content")
+HASH2=$(uwf cas put-text "section 2 content")
+
+# Reference hashes in your frontmatter or in a parent node
+\`\`\`
+
+This enables progressive loading — consumers can fetch the root and resolve children on demand.
+`;
+}

packages/workflow-util/src/index.ts

@@ -1,3 +1,4 @@
+export { generateActorReference } from "./actor-reference.js";
 export { generateArchitectureReference } from "./architecture-reference.js";
 export { encodeUint64AsCrockford } from "./base32.js";
 export { generateCliReference } from "./cli-reference.js";