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-24/client.md

@@ -1,3 +1,12 @@
+---
+title: "Sprint 24 — Client Briefing"
+description: "Character select screen, triangle activation response, news ticker display"
+type: sprint
+status: archived
+sprint: 24
+team: "client"
+---
+
 # Sprint 24: Signal — Client Tasks
 
 **Goal:** Wire the storyteller's activation event into player-visible consequences, thread character archetype through the full session lifecycle, and deliver the first unscripted end-to-end v0.1 playthrough — from main menu to triangle activation.

docs/sprints/sprint-24/copy.md

@@ -1,3 +1,12 @@
+---
+title: "Sprint 24 — Copy Briefing"
+description: "Triangle activation monologue lines, per-archetype proximity content"
+type: sprint
+status: archived
+sprint: 24
+team: "copy"
+---
+
 # Sprint 24: Signal — Copy Tasks
 
 **Goal:** Wire the storyteller's activation event into player-visible consequences, thread character archetype through the full session lifecycle, and deliver the first unscripted end-to-end v0.1 playthrough — from main menu to triangle activation.

docs/sprints/sprint-24/joint.md

@@ -1,3 +1,12 @@
+---
+title: "Sprint 24 — Joint Briefing"
+description: "v0.1 capstone coordination, StartupMessage wire format, end-to-end playthrough proof"
+type: sprint
+status: archived
+sprint: 24
+team: "joint"
+---
+
 # Sprint 24: Signal — Joint / Integration
 
 **Goal:** Wire the storyteller's activation event into player-visible consequences, thread character archetype through the full session lifecycle, and deliver the first unscripted end-to-end v0.1 playthrough — from main menu to triangle activation.

docs/sprints/sprint-24/server.md

@@ -1,3 +1,12 @@
+---
+title: "Sprint 24 — Server Briefing"
+description: "Character archetype spawning, triangle activation consumer, news ticker"
+type: sprint
+status: archived
+sprint: 24
+team: "server"
+---
+
 # Sprint 24: Signal — Server Tasks
 
 **Goal:** Wire the storyteller's activation event into player-visible consequences, thread character archetype through the full session lifecycle, and deliver the first unscripted end-to-end v0.1 playthrough — from main menu to triangle activation.