docs(docs): add frontmatter to all sprint briefings

Standardized YAML frontmatter on all 115 sprint briefing files across
sprints 1-26 with title, description, type, status, sprint number, and
team fields.

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

docs/sprints/sprint-18/client.md

@@ -1,3 +1,12 @@
+---
+title: "Sprint 18 — Client Briefing"
+description: "Minimap rendering, dialogue UI, knowledge/journal display"
+type: sprint
+status: archived
+sprint: 18
+team: "client"
+---
+
 # Sprint 18: Touch — Client Tasks
 
 **Goal:** The player can examine entities and objects to generate character-filtered observations; NPCs detect and react when watched; social actions propagate through the relationship graph; minimap renders POIs on the client.

docs/sprints/sprint-18/copy.md

@@ -1,3 +1,12 @@
+---
+title: "Sprint 18 — Copy Briefing"
+description: "Collision-resistant line IDs for auto-generated NPCs, drama module schema"
+type: sprint
+status: archived
+sprint: 18
+team: "copy"
+---
+
 # Sprint 18: Touch — Copy Tasks
 
 **Goal:** The player can examine entities and objects to generate character-filtered observations; NPCs detect and react when watched; social actions propagate through the relationship graph; minimap renders POIs on the client.

docs/sprints/sprint-18/joint.md

@@ -1,3 +1,12 @@
+---
+title: "Sprint 18 — Joint Briefing"
+description: "Examine mechanic integration, knowledge graph wire format, NPC vision coordination"
+type: sprint
+status: archived
+sprint: 18
+team: "joint"
+---
+
 # Sprint 18: Touch — Joint Tasks
 
 **Goal:** The player can examine entities and objects to generate character-filtered observations; NPCs detect and react when watched; social actions propagate through the relationship graph; minimap renders POIs on the client.

docs/sprints/sprint-18/server.md

@@ -1,3 +1,12 @@
+---
+title: "Sprint 18 — Server Briefing"
+description: "Examine mechanic, NPC player-awareness, character goal framework, social propagation"
+type: sprint
+status: archived
+sprint: 18
+team: "server"
+---
+
 # Sprint 18: Touch — Server Tasks
 
 **Goal:** The player can examine entities and objects to generate character-filtered observations; NPCs detect and react when watched; social actions propagate through the relationship graph; minimap renders POIs on the client.