Add pythonmonkey localExec() evaluator (evaluator-pm)

Mirrors evaluator-node.js's SandboxConstructor contract for pythonmonkey: spawns the sandbox as a separate Python child process (pythonmonkey has no vm.createContext() equivalent, so a second isolated JS global needs a second OS process) and speaks the same wire protocol as lib/standaloneWorker.js. Process/socket management is delegated to evaluator-pm-parent.py via globalThis.python.eval(), since pythonmonkey has no child_process or net module.

Also adds a pythonmonkey entry to the sandbox bootstrap definitions (mirroring node's), and fixes build/bundle to resolve dcpClientDestination via cygpath on Windows, where a bash-style path was getting silently misresolved by node.exe and causing webpack to write its output to the wrong directory.

Co-Authored-By: Claude Sonnet 5 noreply@anthropic.com