builder: require durable workspace execution

agent_builder/skills/agent-quality-review/SKILL.md

@@ -37,6 +37,9 @@ Check these items:
 - Custom subagents that need project skills include their own `skills` field.
 - Deterministic tools do exact work; no fake canned-response tools.
 - File-producing skills call `ctx.write_artifact` and `ctx.emit_artifact`.
+- Commands that create downloadable outputs run through `ctx.workspace_shell`
+  or `ctx.workspace_python` and write under `/workspace/outputs/...`. Plain
+  subprocesses in the agent container are not durable workspace writes.
 - External calls, secrets, workspace access, pricing, and resources are
   declared on the class.