chore: initialize from backend template 0a6dd0e

docs/runbooks/auth-kid-unknown.md

@@ -0,0 +1,34 @@
+---
+title: Runbook — AUTH_KID_UNKNOWN (키 ID 미인식)
+category: AUTH
+error_codes: [AUTH_KID_UNKNOWN]
+severity: P2
+owner: oncall
+last_updated: 2026-06-15
+status: stub
+---
+
+# Runbook: AUTH_KID_UNKNOWN (`runbook://auth/kid-unknown`)
+
+## Symptoms
+
+- HTTP 401 with `error.code=AUTH_KID_UNKNOWN`, `retryable=true`
+- Token `kid` header not present in cached JWKS
+
+## Diagnosis
+
+- Check if IdP key rotation occurred recently
+- Verify JWKS cache TTL and refresh timing
+
+## Action
+
+- Force JWKS cache refresh
+- Confirm new key is published in IdP JWKS endpoint
+
+## Escalation
+
+- Escalate to IdP team if new kid not appearing in JWKS after 10 minutes
+
+---
+
+> **Stub**: Phase D2 — author body after domain adoption. (feature-operational-runbook-contract D9)