Document shell-safe PR comment workflow

[huangruiteng]

Summary

• add a LoopX self-repair pattern for shell command substitution in PR/comment bodies
• pin the pattern in the interaction-pattern smoke so the badcase remains documented

Validation

• python3 examples/interaction-pattern-catalog-smoke.py
• git diff --check
• loopx check --scan-path skills/loopx-self-repair/references/repair-patterns.md --scan-path examples/interaction-pattern-catalog-smoke.py

Notes

This PR intentionally uses a body file for Markdown-rich PR text.

[huangruiteng]

Self-review summary:

• Scope: public self-repair documentation plus a focused smoke assertion only.
• Change: records the shell command-substitution badcase for Markdown-rich PR/comment bodies and recommends single-quoted bodies, stdin/body-file, or connector/API calls.
• Validation passed locally:
  • python3 examples/interaction-pattern-catalog-smoke.py
  • git diff --check
  • loopx check on the two changed paths
• Merge status: normal merge is blocked by branch policy; auto-merge is disabled for this repository.