docs(api): document the v2 execution surface

Adds execute, execution status, and cancel to openapi-v2-workflows.json
with the structured ExecutionError schema (append-only code enum + block
attribution) and the ExecutionResource contract, documenting the rules
that differ from v1: modes are body-selected, a failed run is HTTP 200
with status 'failed', an executionId always means data (never the error
envelope), queued status is visible immediately, and Response-block
payloads stay inside output. Registers the three pages in the generated
workflows meta.json and bumps the route-count baseline.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01CiHhAk2R1NryaS3R8n2yFz

Author: TheodoreSpeaks

apps/docs/content/docs/en/api-reference/(generated)/workflows/meta.json

@@ -6,6 +6,9 @@
     "importWorkflow",
     "deployWorkflow",
     "undeployWorkflow",
-    "rollbackWorkflow"
+    "rollbackWorkflow",
+    "executeWorkflowV2",
+    "getWorkflowExecutionV2",
+    "cancelExecutionV2"
   ]
 }