agent: add agent_job_pending webhook, JS_CANCELLED status and JobState.reason (#1860)

* agent: add agent_job_pending webhook, JS_CANCELLED status and JobState.reason

agent_job_pending reports a dispatched job that is still waiting for an
agent, with JobState.reason saying why (e.g. no capacity). A job that
ends before any agent is assigned is reported as agent_job_ended with
the new JS_CANCELLED status, and the reason distinguishes a closed room
from a deleted dispatch, so it can be told apart from JS_FAILED.

Generated Go/JS bindings are produced by the Generate workflow.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

* generated protobuf

* agent: add JSR_RETRYING job state reason

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

* generated protobuf

---------

Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>
Co-authored-by: github-actions <41898282+github-actions[bot]@users.noreply.github.com>

Author: 3 people

.changeset/agent-job-pending-webhook.md

@@ -0,0 +1,6 @@
+---
+"github.com/livekit/protocol": patch
+"@livekit/protocol": patch
+---
+
+Add `agent_job_pending` webhook event, `JS_CANCELLED` job status, and `JobState.reason` (including `JSR_RETRYING`)

livekit/livekit_agent.pb.go

@@ -47,6 +47,8 @@ message JobState {
   string participant_identity = 6;
   string worker_id = 7 [(logger.name) = "workerID"];
   string agent_id = 8 [(logger.name) = "agentID"];
+  // why the job has no agent, for JS_PENDING and JS_CANCELLED jobs
+  JobStateReason reason = 9;
 }
 
 // from Worker to Server
@@ -101,6 +103,20 @@ enum JobStatus {
   JS_RUNNING = 1;
   JS_SUCCESS = 2;
   JS_FAILED = 3;
+  // the job ended before it was assigned to an agent
+  JS_CANCELLED = 4;
+}
+
+enum JobStateReason {
+  JSR_UNSPECIFIED = 0;
+  // no agent was available to accept the job
+  JSR_NO_CAPACITY = 1;
+  // the room closed before an agent was assigned
+  JSR_ROOM_CLOSED = 2;
+  // the dispatch was deleted before an agent was assigned
+  JSR_DISPATCH_DELETED = 3;
+  // the job failed and is being dispatched again
+  JSR_RETRYING = 4;
 }
 
 message SimulateJobRequest {