Normalize agent instructions and workplan frontmatter (STATE-WP-0067)

- Align agent files with on-disk workplan prefixes (infer from workplan ids)
- Set workplan domain to registered domain_slug; add topic_slug where applicable
- Repair frontmatter delimiter formatting; migrate legacy task status literals
- Regenerate AGENTS.md, CLAUDE.md, and .claude/rules from State Hub templates

workplans/KONT-WP-0003-engine-implementation.md

@@ -2,7 +2,7 @@
 id: KONT-WP-0003
 type: workplan
 title: "Headless Knowledge Engine Implementation"
-domain: markitect
+domain: communication
 repo: kontextual-engine
 status: done
 owner: codex