feat(seer): Record agent_handoff analytics in launch_coding_agents_for_run (#112516)

## Summary
- Adds `ai.autofix.agent_handoff` analytics event to
`launch_coding_agents_for_run`, which was previously only recorded in
`trigger_coding_agent_handoff` (on-completion hook path)
- Adds a `referrer` parameter to distinguish the source:
`api.organization_coding_agents` (user-initiated from UI),
`seer_rpc.trigger_coding_agent_launch` (seer-initiated), or the existing
`autofix.on_completion_hook` (automation)
- This ensures all coding agent launches (Cursor, Claude Code, GitHub
Copilot) are tracked in BigQuery regardless of trigger path

## Test plan
- [ ] Verify existing tests pass
- [ ] Confirm `ai.autofix.agent_handoff` events appear in BigQuery with
the new referrer values after deploy


Agent transcript:
https://claudescope.sentry.dev/share/K0dXID_ySuOGsHj7b4N5JYUuP88VYoij1v1UHwMd8CA

Author: JoshFerge

src/sentry/analytics/events/autofix_events.py

@@ -72,6 +72,7 @@ class AiAutofixPrCreatedCompletedEvent(AiAutofixPhaseEvent):
 @analytics.eventclass("ai.autofix.agent_handoff")
 class AiAutofixAgentHandoffEvent(AiAutofixPhaseEvent):
     coding_agent: str | None
+    initiator: str | None = None
 
 
 analytics.register(AiAutofixRootCauseStartedEvent)

src/sentry/integrations/api/endpoints/organization_coding_agents.py

@@ -153,6 +153,7 @@ def post(self, request: Request, organization: Organization) -> Response:
             trigger_source=trigger_source,
             instruction=instruction,
             user_id=request.user.id,
+            initiator="user",
         )
 
         successes = results["successes"]

src/sentry/seer/autofix/autofix_agent.py

@@ -576,6 +576,7 @@ def trigger_coding_agent_handoff(
             group_id=group.id,
             referrer=referrer.value,
             coding_agent=coding_agent_name,
+            initiator="automation",
         )
     )
 

src/sentry/seer/autofix/coding_agent.py

@@ -11,7 +11,7 @@
 from requests import HTTPError
 from rest_framework.exceptions import APIException, NotFound, PermissionDenied, ValidationError
 
-from sentry import features
+from sentry import analytics, features
 
 
 class IntegrationNotFound(NotFound):
@@ -30,6 +30,7 @@ class StateReposNotFound(NotFound):
     pass
 
 
+from sentry.analytics.events.autofix_events import AiAutofixAgentHandoffEvent
 from sentry.constants import ENABLE_SEER_CODING_DEFAULT, ObjectStatus
 from sentry.integrations.claude_code.integration import (
     ClaudeCodeIntegrationMetadata,
@@ -419,6 +420,7 @@ def launch_coding_agents_for_run(
     trigger_source: AutofixTriggerSource = AutofixTriggerSource.SOLUTION,
     instruction: str | None = None,
     user_id: int | None = None,
+    initiator: str | None = None,
 ) -> dict[str, list]:
     """
     Launch coding agents for an autofix run.
@@ -513,6 +515,18 @@ def launch_coding_agents_for_run(
         },
     )
 
+    coding_agent_name = provider or (integration.provider if integration else None)
+    analytics.record(
+        AiAutofixAgentHandoffEvent(
+            organization_id=organization.id,
+            project_id=autofix_state.request.project_id,
+            group_id=autofix_state.request.issue["id"],
+            referrer=None,
+            coding_agent=coding_agent_name,
+            initiator=initiator,
+        )
+    )
+
     return results
 
 

src/sentry/seer/endpoints/seer_rpc.py

@@ -601,6 +601,7 @@ def trigger_coding_agent_launch(
             integration_id=integration_id,
             run_id=run_id,
             trigger_source=AutofixTriggerSource(trigger_source),
+            initiator="seer_agent",
         )
         return {"success": True}
     except IntegrationNotFound: