[BUG] Windows Desktop: idle/closed Code sessions keep their MCP servers alive — 121 node processes, ~10 GB RAM (regression of #58915?)

Environment: Windows 11 Pro 26200, Claude Desktop 2.31226.1.0 (MSIX), Claude Code 2.1.295

Observed: With ~2 sessions actually in use but more chats opened during the day, there were 8 live claude.exe session processes. Each one keeps its own full set of MCP servers (~15 stdio servers launched via cmd /c npx ...):

• 121 node.exe processes, ~10 GB private memory
• 123 cmd.exe + 96 conhost.exe wrappers
• committed memory 34.5 GB on a 31 GB machine

Switching to another chat or leaving a session idle does not stop its claude.exe or its MCP children. Only restarting the app frees the memory.

Expected: Inactive/closed sessions release their MCP servers (or idle-timeout them), or stdio servers are shared across sessions.

Related: #58915 (same symptom on macOS, closed as completed on 2026-05-19), #1935, #33947.