No docs-only pull requests to main

Owner policy (billing): Do not open a GitHub pull request to main whose only changes are under docs/ (handoffs, parity matrices, playbooks, AGENT-INTEGRATION.md, etc.).

• Ship documentation updates in the same PR as the code, tests, or CI they belong to (e.g. Track B3 memory wiring + updated docs/NEXT-SESSION-HOSTED-HUB-MCP.md together).
• It is fine to commit and git push handoff edits on a long-lived feature branch (e.g. feat/hosted-mcp-prompts-b3) so work is saved and shareable — just do not open a merge-to-main PR for docs alone.
• If the user asks only to “update the handoff,” update files on the current feature branch and stop; do not create a PR unless they explicitly request a merge that includes non-doc changes.