show thread context for likes and teach phi that owner-like = approval
two fixes for like-as-authorization:
1. engagement entries now render thread context in the notifications
block, so phi can see what conversation a liked post belongs to
2. operational instructions explicitly state that an owner like on an
authorization request means "do the thing"
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>