[taigrr]

Summary

• Cover default timeout policy: disabled/non-positive timeouts, parent cancellation, caller deadlines on either side of the configured timeout, and caller context ownership.
• Exercise real subprocess cancellation through both StartServer and Device.Shell, verifying DeadlineExceeded remains wrapped in CommandError.
• Bound hanging regressions with a cancellation watchdog; no runtime or dependency changes.

Validation

• Baseline and final go test -race ./...
• go vet ./..., staticcheck ./..., golangci-lint run ./... (zero issues)
• golangci-lint fmt --diff, go build ./..., go generate ./..., git diff --check
• Mutation check: disabling default timeouts makes both command regressions fail; source restored afterward.

Independent of open IPv6 and toolchain/example dependency PRs.