CLI: add `--json` output to `nora workspaces list`

[JustinaChano04]

Area: cli/ · Difficulty: trivial

Problem

nora doctor already supports --json, and there is an open issue to add --json to the agents/monitoring commands, but nora workspaces list still only renders the table view. That makes scripting workspace discovery awkward even though the underlying command already receives raw JSON from GET /api/workspaces.

Scope

Add an optional --json flag to list() in cli/src/commands/workspaces.js. When the flag is set, print the raw JSON payload and skip table rendering. Mirror the same flag-reading pattern used in cli/src/commands/doctor.js. Update cli/README.md so the workspace command docs mention the new machine-readable output.

Acceptance

• nora workspaces list --json emits valid JSON.
• nora workspaces list without the flag remains unchanged.
• cli/README.md documents the flag.

Why this is a good first issue

Very small CLI enhancement, existing doctor pattern to copy, and a crisp done-state with low code risk.

[solomon2773]

Thanks @JustinaChano04 — I verified current master still renders only the table path for workspaces list, so the JSON-output gap remains. This issue is open and unassigned. A contributor can claim it here; please cover both the new JSON path and unchanged table behavior, then update the CLI README and report CLI tests.