Add host-managed tmux support

[daniel-kindl]

Goal

Add tmux to dk-devkit as a host-level terminal session manager for the workstation.

The intended architecture is:

Konsole
  -> tmux on host
      -> host shell / Distrobox
          -> Pi / Codex / Claude / project tooling

tmux should be installed once on the host and used across development environments. It should not be duplicated inside individual Distrobox containers unless a container has a specific independent need for it.

Scope

• Add tmux to the host CLI package manifest.
• Create a dedicated tmux component if that matches the existing component model better than keeping it only under host-cli-tools.
• Add version-controlled tmux configuration under config/tmux/.
• Install/link the managed configuration into the user's home directory in an idempotent way.
• Include the tmux component in the daniel workstation profile.
• Add verification/doctor coverage for:
  • tmux is available on the host.
  • the expected config is active.
  • repeated installation does not create duplicate or conflicting state.
• Document the intended host -> tmux -> Distrobox workflow.

Initial configuration

Keep the first configuration conservative and close to upstream defaults. Useful baseline settings to evaluate:

• sensible scrollback/history size
• mouse support
• true-color / modern terminal compatibility
• pane/window navigation that does not conflict with common shell or editor bindings
• clipboard behavior under KDE/Wayland
• Distrobox-friendly shells and environment inheritance

Avoid large plugin frameworks or opinionated keybinding schemes in the first iteration. The configuration should remain understandable and owned directly by dk-devkit.

Acceptance criteria

• A fresh dk-devkit workstation setup installs tmux on the host.
• tmux is available from Konsole without entering a Distrobox.
• The managed tmux configuration is reproducible from the repository.
• A tmux session can host both host shells and shells entered through distrobox enter.
• Existing Distrobox/container manifests do not gain redundant tmux installations.
• Existing bootstrap/install/verify flows remain idempotent and pass.