docs(work): close sandcastle-subscription-auth-v1 epic

docs/work/sandcastle-subscription-auth-v1/_epic.md

@@ -3,7 +3,7 @@ id: sandcastle-subscription-auth-v1
 prd: null
 title: Sandcastle subscription auth as primary flow
 type: epic
-status: in-progress
+status: done
 features: [tooling, ci]
 created: 2026-05-13
 ---
@@ -26,4 +26,4 @@ spends zero per-task agent tokens for Pro/Max subscribers.
 
 ## Stories
 
-- [ ] [01 — Subscription-first dispatch + Dockerfile + docs](01-subscription-first/_story.md)
+- [x] [01 — Subscription-first dispatch + Dockerfile + docs](01-subscription-first/_story.md)