`internal/mcp/transport.go` used syscall.Setpgid and syscall.Kill
unconditionally, both Unix-only. Split the platform bits into
`transport_unix.go` (build tag `!windows`) keeping the existing
process-group semantics, and `transport_windows.go` (build tag
`windows`) falling back to `os.Process.Kill` (kills only the
immediate process — full process-tree kill on Windows would need
golang.org/x/sys/windows + job objects, deferred).
Caught by `goreleaser release --snapshot` cross-compiling for
windows/amd64 and windows/arm64.
vikingowl
67948df8cb