fix(skills): remove checkpoint helper dead code

skills/develop/develop-workflow/scripts/checkpoint-record.mjs

@@ -184,13 +184,12 @@ async function readExisting(io, target) {
 }
 
 async function openUniqueTemp(io, target) {
-  const directory = dirname(target);
   for (let attempt = 0; attempt < MAX_TEMP_NAME_ATTEMPTS; attempt += 1) {
     const id = io.randomUUID();
     const path = `${target}.tmp-${process.pid}-${id}`;
     try {
       const handle = await io.open(path, "wx", FILE_MODE);
-      return { path, handle, directory };
+      return { path, handle };
     } catch (error) {
       // A collision is not stale-file cleanup. Leave the old file alone and try a new name.
       if (isAlreadyExists(error)) continue;

skills/develop/develop-workflow/tests/checkpoint-record.test.mjs

@@ -12,7 +12,6 @@ import {
   checkpointRecord,
   defaultIo,
   REQUIRED_SECTIONS,
-  validateRecord,
 } from "../scripts/checkpoint-record.mjs";
 
 const scriptPath = fileURLToPath(new URL("../scripts/checkpoint-record.mjs", import.meta.url));