Use positive bootstrap proof guidance

[chubes4]

Summary

• Rephrase the Docs Agent bootstrap proof instruction around the desired successful output.
• Keep the proof requirement as an opened PR while avoiding negative no-op wording in the run prompt.

Testing

• bash -n tests/playground-ci/scripts/run-docs-agent.sh
• git diff --check

AI assistance

• AI assistance: Yes
• Tool(s): OpenCode (GPT-5.5)
• Used for: Updated the Docs Agent consumer bootstrap wording and ran targeted validation.