Accept non-UUID triggering_event_id and add GitOps runbook

Broaden POST /issues/ so triggering_event_id is any non-empty traceability
string, enabling cron/scheduled activity-core emissions with stable keys like
"scheduled" while event-driven paths still send UUIDs. Document the railiance01
ArgoCD deployment path in docs/argocd-gitops.md and update ISSUE-WP-0003 task
status to reflect repo-side progress.

issue_core/api/schemas.py

@@ -2,14 +2,12 @@
 Pydantic schemas for the issue-core REST API.
 
 The TaskIngestionRequest schema matches activity-core's IssueSink TaskSpec
-payload exactly. See:
+payload. See:
   - SCOPE.md "TaskSpec payload" section
   - activity-core docs/adr/adr-001-event-bridge-architecture.md
 """
 
 from typing import List, Literal, Optional
-from uuid import UUID
-
 from pydantic import BaseModel, ConfigDict, Field
 
 
@@ -31,7 +29,14 @@ class TaskIngestionRequest(BaseModel):
     due_in_days: Optional[int] = Field(default=None, ge=0)
     source_type: SourceType
     source_id: str = Field(..., min_length=1)
-    triggering_event_id: UUID
+    triggering_event_id: str = Field(
+        ...,
+        min_length=1,
+        description=(
+            "Activity event UUID, or a stable scheduler/source key when no "
+            "event row exists."
+        ),
+    )
     activity_definition_id: str = Field(..., min_length=1)