Build TUI MVP with command preview and dry-run

[github-actions]

Summary

Build the initial Terminal.Gui-based TUI with work item workflows, command preview,
and a global dry-run toggle for discoverability.

Acceptance criteria

• TUI provides basic work item workflows defined in the spec (list, view, create, update).
• Bottom status line shows the last command invoked by the TUI.
• Global dry-run toggle is visible and marks outputs as dry-run.
• Errors surface CLI validation messages in dialogs.
• Spec and ADR links are up to date.

Related

• Specs:
  • feature-spec-terminal-ui
• ADRs:
  • ADR-2025-12-30-terminal-ui-mode-in-cli-executable