product: keep CLI helpers secondary to TUI workflows

[nathanhuh]

Summary

Unic should remain a TUI-first AWS operations tool. CLI helpers are acceptable when they support scripting, automation, or copy/paste workflows, but new user-facing AWS service capabilities should be discoverable and usable from the TUI first.

Context

• feat: add ECR login helper #177 currently frames the ECR login helper as CLI-first.
• feat: add ECR login helper #165 allows a TUI or CLI implementation, which is too loose for the product direction.
• The intended product posture is TUI-first, with CLI commands as secondary support surfaces where useful.

Scope

• Define the product rule that new service workflows default to a TUI entry point.
• Treat CLI commands as optional secondary surfaces for automation or direct command generation.
• Update README and relevant docs so CLI examples do not become the primary feature framing.
• Update feat: add ECR login helper #165 or its implementation so ECR login is TUI-first, with any CLI helper positioned as secondary.
• Add review guidance so future PRs do not ship service features as CLI-first unless there is an explicit exception.

Acceptance Criteria

• TUI-first guidance is documented in README and/or project docs.
• ECR login is available through the TUI as the primary workflow.
• Any ECR CLI command is documented as secondary or automation-oriented.
• Future service feature issues and PRs have a clear TUI-first expectation.

Related

• feat: add ECR login helper #165
• feat: add ECR login helper #177