Implement full dialogue selection pipeline (D-028): 4-layer filtering
engine with access tier, situation derivation, trust tier, and weighted
topic+mood scoring via SimRng. Add ContentSlug component for stable
content identity across save/load. Add walk-away KG recording with
IncompleteInteraction events per D-064 three-phase consequences. Bump
protocol to v8 with DialogueResponseEvent. Fixes#305, #427, #452.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>