Add TCP transport for ollmfilesd RPC

[roojs]

Summary

• Add a shared TCP RPC listener for ollmfilesd on loopback port 4141.
• Keep one shared OLLMrpc.Client implementation for Unix and TCP; platform files only provide defaults/connectors.
• Let Linux opt into TCP with tcp:// / --tcp, while keeping Unix socket behavior as the default.
• Make Windows default to TCP and start ollmfilesd --tcp through the Windows starter.
• Add a Linux TCP smoke test and stage ollmfilesd.exe plus required RPC/vector DLLs in the Windows bundle.
• Fix RPC script-mode response draining and client pending-response cleanup races found during validation.

Testing

• ninja -C build
• meson test -C build test-rpc test-rpc-t1 test-rpc-tcp --print-errorlogs