Add tree-kill via taskkill /T /F in processRunner and codexAppServerManager so timeout enforcement and session stop properly terminate the entire process tree instead of just the cmd.exe wrapper. Detect Windows command not found (exit 9009) in normalizeExitError. Pre-validate editor commands with isCommandAvailable in open.ts before spawning. Fix ProviderHealth test import and dev-runner test path assertion for Windows.

Made-with: Cursor