Workspace refactor feature spec

[zachcasper]

Description

This is a feature spec for refactoring the rad CLI workspace to be easier to use and understand.

Type of change

• This pull request is a minor refactor, code cleanup, test improvement, or other maintenance task and doesn't change the functionality of Radius (issue link optional).

Contributor checklist

Please verify that the PR meets the following requirements, where applicable:

• An overview of proposed schema changes is included in a linked GitHub issue.
  • Yes
  • Not applicable
• A design document PR is created in the design-notes repository, if new APIs are being introduced.
  • Yes
  • Not applicable
• The design document has been reviewed and approved by Radius maintainers/approvers.
  • Yes
  • Not applicable
• A PR for the samples repository is created, if existing samples are affected by the changes in this PR.
  • Yes
  • Not applicable
• A PR for the documentation repository is created, if the changes in this PR affect the documentation or any user facing updates are made.
  • Yes
  • Not applicable
• A PR for the recipes repository is created, if existing recipes are affected by the changes in this PR.
  • Yes
  • Not applicable

[Copilot]

Pull request overview

Adds a CLI feature specification design note proposing to replace the user-facing “workspace” concept with per–kube-context defaults managed via rad configure --defaults, while keeping legacy workspaces: data as read-only compatibility for --workspace.

Changes:

• Introduces a new feature spec describing UX rationale and command surface (rad configure --defaults, --list-defaults).
• Defines config schema changes (defaults: keyed by kube context) and a per-key precedence/resolution order with legacy fallback.
• Documents user stories, edge cases, and functional requirements (including concurrency/atomic-write expectations).