fix(run-multiple): avoid temp.mjs filename collision across forked processes

When run-multiple forks N concurrent processes, each process transpiles the
same .ts files (config, helpers, includes) to identically named *.temp.mjs
files. A process that finishes first deletes its temp file, causing other
processes that haven't imported it yet to fail with "Cannot find module
*.temp.mjs".

Fix: embed process.pid in the temp filename so every worker writes its own
isolated copy. Cleanup still works because allTempFiles is built from
transpiledFiles.values(), which already contains the pid-suffixed paths.
The .includes('.temp.mjs') substring check in step/base.js continues to
match the new *.{pid}.temp.mjs filenames.

Fixes #5642

Author: kapilvus

lib/utils/typescript.js

@@ -385,7 +385,9 @@ const __dirname = __dirname_fn(__filename);
     )
 
     // Write the transpiled file with updated imports
-    const tempFile = filePath.replace(/\.ts$/, '.temp.mjs')
+    // Use process.pid in the filename to avoid collisions when run-multiple forks
+    // several processes that all transpile the same .ts files concurrently.
+    const tempFile = filePath.replace(/\.ts$/, `.${process.pid}.temp.mjs`)
     fs.writeFileSync(tempFile, jsContent)
     transpiledFiles.set(filePath, tempFile)
   }