fix(skill): check merge conflicts in pull-request convergence loop #3707

Problem

The /pull-request skill convergence loop (section 6) only checks mergeable status at the stop condition (6f). If a merge conflict appears mid-loop (e.g. from concurrent pushes to master), the skill keeps iterating without detecting it.

Proposed fix

Add a mergeable check early in the loop (after CI passes, before reading feedback). If CONFLICTING, stop the loop and report to user instead of continuing to iterate uselessly.

  1. Wait for CI
  2. If CI fails → fix, push, GOTO 1
  2b. Check mergeable → if CONFLICTING, report to user and STOP
  3. Grace period → ...

Files to modify

• .claude/skills/pull-request/SKILL.md — add step 2b in loop procedure + update 6f