feat: Add tags and container_image to Sandbox

[iiilisan]

Expose Sandbox.tags and Sandbox.container_image properties from
Start/Get/List responses. Refactor cwsandbox ls into table/wide/json
output modes: default shows ID, status, image, started_at; wide adds
tower, tower group, runway, tags.

cwsandbox ls        
SANDBOX ID                               STATUS         IMAGE                     STARTED AT              
---------------------------------------- -------------- ------------------------- ------------------------
17bcd812-c1ee-43db-a9ee-4f6f98503847     running        python:3.11               2026-04-01 15:49:39 UTC 

cwsandbox ls -o wide
SANDBOX ID                               STATUS         IMAGE                     STARTED AT               TOWER                TOWER GROUP          RUNWAY               TAGS
---------------------------------------- -------------- ------------------------- ------------------------ -------------------- -------------------- -------------------- ----------------------------------------
17bcd812-c1ee-43db-a9ee-4f6f98503847     running        python:3.11               2026-04-01 15:49:39 UTC  dev-1                -                    default              interactive,streaming

cwsandbox ls -o json
[
  {
    "sandbox_id": "17bcd812-c1ee-43db-a9ee-4f6f98503847",
    "status": "running",
    "tower_id": "dev-1",
    "runway_id": "default",
    "tower_group_id": null,
    "started_at": "2026-04-01T15:49:39.237815",
    "container_image": "python:3.11",
    "tags": [
      "interactive",
      "streaming"
    ]
  }
]

Closes #65