feat(apiserver): surface human-readable job ID (fmt_jobid form) in responses

The MCP/apiserver returned the raw 64-bit job ID (e.g. 73930964699447296)
while xce_test/xcecli display the dash form (e.g. 1-0-1786585485-0) that
parse_jobid accepts. A user taking the numeric form into xce_test fails to
parse it. The apiserver is the data-correctness owner (MCP only reads), so
it now emits the controller's fmt_jobid form alongside the numeric ID:

- models: JobSubmitResponse gains job_id_human; job list rows gain
  job_id_human (processJobData), using the existing backend.FormatJobID.
- schedulerclient: URMJob.HumanID + SubmitJobResult.JobIDHuman parse it.
- Tests: backend.FormatJobID (real t1 job, pre-cluster1 job, array child);
  processJobData adds job_id_human.

Also rename the SSE permission event:subscribe → event:view so mcp_readonly
stays strictly *:view (the read-only invariant test enforces).

Verified live on t1: scheduler_submit returns job_id_human 1-0-1786586474-0
and scheduler_get_job returns human_id.

Co-Authored-By: Claude <noreply@anthropic.com>

src/frontend/schedulerclient/write.go

@@ -36,9 +36,10 @@ type JobSpec struct {
 
 // SubmitJobResult is the apiserver's response to a successful job submission.
 type SubmitJobResult struct {
-	JobID     int64  `json:"jobid"` // NB: lowercase field name in the apiserver response
-	QueueName string `json:"queue_name"`
-	Message   string `json:"message"`
+	JobID      int64  `json:"jobid"` // NB: lowercase field name in the apiserver response
+	JobIDHuman string `json:"job_id_human"` // cluster-apiserver-timestamp-seq (usable in xce_test/xcecli)
+	QueueName  string `json:"queue_name"`
+	Message    string `json:"message"`
 }
 
 // JobControlRequest is the body sent to POST /xce/v1/jobs/:jobids/control.