add branching explanation to prompt

services/workflow_chat/gen_project_prompts.yaml

@@ -141,6 +141,7 @@ prompts:
     2. Each subsequent job should connect to the previous job with one condition_type: on_job_success, on_job_failure, always or js_expression (for the latter, also add a condition_expression in quotes e.g. '!state.error')
     3. For branching workflows, create conditional edges as appropriate
     4. Edges should be enabled by default
+    5. Edges execute simultaneously and independently. When multiple edges target the same job (e.g., job-3 receives edges from both job-1 and job-2), that target job will run once per incoming edge. If job-1 and job-2 both succeed, job-3 executes twice—once triggered by each edge. This is not a merge or wait operation; each edge fires its target independently when its condition is met.
 
     ## Do NOT fill in job code