[Reverted Setup Linux] Enable system reset on Linux hosts

[krotz-dieter]

Problem

k2s system reset is blocked for Linux-only installations by the command handler, although the Linux system provider already implements reset through kubeadm reset -f.

This is an inconsistent command/provider boundary: a native implementation exists but is unreachable from the CLI. It also leaves Linux users without the standard recovery path after a failed or incomplete installation.

Proposed Solution

Allow k2s system reset to call System.Reset on Linux hosts. Define Linux reset semantics clearly, including cleanup of Kubernetes control-plane state, CNI interfaces, and K2s runtime configuration where appropriate.

Preserve the existing Windows behavior and do not route Linux execution through PowerShell.

Relevant Files

• cmd/k2s/cmd/system/reset/reset.go
• cmd/k2s/cmd/system/reset/network.go
• internal/provider/system_linux.go
• internal/setuporchestration/orchestrator_linux.go

Acceptance Criteria

• k2s system reset is available after k2s install --linux-only.
• The command invokes the Linux provider rather than returning a Linux-only availability error.
• Reset cleans up the kubeadm control plane and reports any cleanup failures clearly.
• k2s system reset network is validated and documented for Linux-host behavior.
• Unit tests prove Linux command routing and preserve the existing Windows behavior.
• An integration test verifies that a reset Linux host can be installed again cleanly.