docs(docs): add frontmatter to all design docs

Standardized YAML frontmatter on all 40 docs/design/ files with title,
description, type, status, ticket, decision_refs, and author fields.
Covers specs, wireframes, voice cards, spatial layouts, and system
designs.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

docs/design/tell-visual-expression.md

@@ -1,3 +1,15 @@
+---
+title: "Tell Visual/Behavioral Expression"
+description: "Specification for five NPC tell categories mapped to Tier 2 movement behaviours with intensity scaling"
+type: design
+status: active
+ticket: "#251"
+decision_refs: [D-016, D-024, D-033, D-044, D-047]
+author: "Araminta"
+created: 2026-02-20
+updated: 2026-03-05
+---
+
 # Tell Visual/Behavioral Expression — Specification
 
 **Version:** v0.1 (Sprint 14)