refactor(subagent): split extension into modules

src/tools.ts

@@ -0,0 +1,65 @@
+import { Type } from "typebox";
+import { FINALIZE_TOOL_NAME } from "./constants.ts";
+import type { PromptConfig, SubagentFinalizePayload } from "./types.ts";
+import { FinalizeStatus } from "./types.ts";
+
+// Resolve Tools - Use exactly one permission mode. approved_tools/allowed_tools
+// is a whitelist; denied_tools is a blacklist over the currently active tools.
+export function resolveTools(
+  agent: PromptConfig,
+  activeTools: string[],
+): string[] {
+  const withoutDelegationTools = (tools: string[]) =>
+    tools.filter((tool) => tool !== "subagent" && tool !== FINALIZE_TOOL_NAME);
+
+  const resolved =
+    agent.approvedTools.length > 0
+      ? withoutDelegationTools([...new Set(agent.approvedTools)])
+      : withoutDelegationTools(
+          [...new Set(activeTools)].filter(
+            (tool) => !new Set(agent.deniedTools).has(tool),
+          ),
+        );
+
+  return [...new Set([...resolved, FINALIZE_TOOL_NAME])];
+}
+
+// Validate Finalize Payload - Keep the parent contract strict and small.
+export function validateFinalizePayload(
+  value: unknown,
+): SubagentFinalizePayload | null {
+  if (!value || typeof value !== "object") return null;
+  const payload = value as Record<string, unknown>;
+  if (payload.status === FinalizeStatus.SUCCESS) {
+    return typeof payload.result === "string" && payload.result.trim()
+      ? { status: FinalizeStatus.SUCCESS, result: payload.result }
+      : null;
+  }
+  if (payload.status === FinalizeStatus.ERROR) {
+    const result =
+      typeof payload.result === "string" ? payload.result : undefined;
+    return typeof payload.error === "string" && payload.error.trim()
+      ? { status: FinalizeStatus.ERROR, error: payload.error, result }
+      : null;
+  }
+  return null;
+}
+
+export const SubagentParams = Type.Object({
+  agent: Type.String({
+    description: "Name of the prompt-defined subagent to invoke",
+  }),
+  task: Type.String({ description: "Task to delegate to the subagent" }),
+  sessionId: Type.Optional(
+    Type.String({
+      description:
+        "Optional sticky subagent session id. Reuse to continue a previous subagent context.",
+    }),
+  ),
+  cwd: Type.Optional(
+    Type.String({
+      description:
+        "Working directory for the subagent process. Defaults to current cwd.",
+    }),
+  ),
+});