refactor: rename status to $status, default to _ when absent

- evaluate() reads $status instead of status, defaults to _ when missing
- Update all YAML examples and .workflows to use $status
- Update cli-workflow resolveEvaluateArgs to use $status
- 10 moderator tests pass including new default _ test
- Single-exit roles no longer need to declare status field

Phase 1 of #499 (closes #500)

packages/cli-workflow/src/__tests__/solve-issue-tea-worktree.test.ts

@@ -81,7 +81,7 @@ describe("solve-issue workflow: tea pr create worktree fix", () => {
     expect(workflow.roles.committer?.frontmatter).toBeDefined();
   });
 
-  test("committer frontmatter schema should require status field", async () => {
+  test("committer frontmatter schema should require $status field", async () => {
     const yamlContent = await readFile(workflowPath, "utf-8");
     // Parse as any to access the raw YAML structure (frontmatter is inline JSON Schema in YAML)
     // eslint-disable-next-line @typescript-eslint/no-explicit-any
@@ -90,8 +90,8 @@ describe("solve-issue workflow: tea pr create worktree fix", () => {
     const frontmatter = workflow.roles.committer?.frontmatter;
     expect(frontmatter).toBeDefined();
     expect(frontmatter?.type).toBe("object");
-    expect(frontmatter?.properties?.status).toBeDefined();
-    expect(frontmatter?.properties?.status?.enum).toContain("committed");
-    expect(frontmatter?.required).toContain("status");
+    expect(frontmatter?.properties?.["$status"]).toBeDefined();
+    expect(frontmatter?.properties?.["$status"]?.enum).toContain("committed");
+    expect(frontmatter?.required).toContain("$status");
   });
 });

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

@@ -669,14 +669,16 @@ function formatThreadReadMarkdown(options: {
   return parts.join("\n\n---\n\n");
 }
 
-type EvaluateLastOutput = Record<string, unknown> & { status: string };
+type EvaluateLastOutput = Record<string, unknown>;
+
+const STATUS_KEY = "$status";
 
 function resolveEvaluateArgs(
   uwf: UwfStore,
   chain: ChainState,
 ): { lastRole: string; lastOutput: EvaluateLastOutput } {
   if (chain.headIsStart) {
-    return { lastRole: START_ROLE, lastOutput: { status: "_" } };
+    return { lastRole: START_ROLE, lastOutput: { [STATUS_KEY]: "_" } };
   }
 
   const lastStep = chain.stepsNewestFirst[0];
@@ -689,11 +691,10 @@ function resolveEvaluateArgs(
     typeof raw === "object" && raw !== null && !Array.isArray(raw)
       ? (raw as Record<string, unknown>)
       : {};
-  const status = typeof base.status === "string" ? base.status : "_";
 
   return {
     lastRole: lastStep.role,
-    lastOutput: { ...base, status },
+    lastOutput: base,
   };
 }