WIP/Draft: Adds a describe command for activities

[davidporter-id-au]

What was changed

This adds a describe command for activities.

Why?

I don't think there's presently a subcommand for this? Moreover, I was hoping to surface / test some information about activity descriptions, and so this seemed a reasonable addition.

2. How was this tested:

./temporal activity describe --activity-id standalone_activity_helloworld_ActivityID1776838201
Activity Info:
  ActivityId              standalone_activity_helloworld_ActivityID1776838201
  RunId                   019db3cf-51e5-7ce8-94a5-592123a7808d
  Type                    Activity
  Status                  Completed
  RunState                Unspecified
  TaskQueue               standalone-activity-helloworld
  Attempt                 1
  ScheduleTime            38 minutes ago
  LastStartedTime         38 minutes ago
  CloseTime               38 minutes ago
  ExpirationTime          36 minutes ago
  ScheduleToCloseTimeout  1m40s
  StartToCloseTimeout     1m40s
  LastWorkerIdentity      34663@dps-MacBook-Pro.local@
  StateTransitionCount    3

./temporal activity describe --activity-id standalone_activity_helloworld_ActivityID1776838201  --output json
{
  "runId": "019db3cf-51e5-7ce8-94a5-592123a7808d",
  "info": {
    "activityId": "standalone_activity_helloworld_ActivityID1776838201",
    "runId": "019db3cf-51e5-7ce8-94a5-592123a7808d",
    "activityType": {
      "name": "Activity"
    },
    "status": "ACTIVITY_EXECUTION_STATUS_COMPLETED",
    "taskQueue": "standalone-activity-helloworld",
    "scheduleToCloseTimeout": "100s",
    "scheduleToStartTimeout": "100s",
    "startToCloseTimeout": "100s",
    "heartbeatTimeout": "0s",
    "retryPolicy": {
      "initialInterval": "1s",
      "backoffCoefficient": 2,
      "maximumInterval": "100s"
    },
    "lastStartedTime": "2026-04-22T06:10:01.840571Z",
    "attempt": 1,
    "executionDuration": "0.017581s",
    "scheduleTime": "2026-04-22T06:10:01.829881Z",
    "expirationTime": "2026-04-22T06:11:41.829881Z",
    "closeTime": "2026-04-22T06:10:01.847462Z",
    "lastWorkerIdentity": "34663@dps-MacBook-Pro.local@",
    "lastAttemptCompleteTime": "2026-04-22T06:10:01.847358Z",
    "stateTransitionCount": "3",
    "stateSizeBytes": "830",
    "searchAttributes": {},
    "header": {}
  },
  "longPollToken": "CiQ1NWI3NzhkZi1kYzMyLTQ3NmItYTg0OC1lNGM1NjVjNWVmMzkSM3N0YW5kYWxvbmVfYWN0aXZpdHlfaGVsbG93b3JsZF9BY3Rpdml0eUlEMTc3NjgzODIwMRokMDE5ZGIzY2YtNTFlNS03Y2U4LTk0YTUtNTkyMTIzYTc4MDhkIOKwg7UMKgIQAzoCEAE="
}

4. Any docs updates needed?

Not sure yet, to be determined

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[CLAassistant]

Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you sign our Contributor License Agreement before we can accept your contribution.
_{You have signed the CLA already but the status is still pending? Let us recheck it.}