docs(memory): clarify Hermes versus MemSearch recall impact

[dommonkhouse]

Summary

• add guidance to memory-recall skills for explaining Hermes versus MemSearch impact
• distinguish runtime behaviour from infrastructure health

Verification

• git diff --check origin/main..HEAD
• scanned diff additions for user-specific local paths

[dommonkhouse]

Ready for maintainer review and merge. I verified this PR is non-draft, mergeable, and has no configured checks reporting failures.