Sentry Alerts for Jomonsho（日本語）

前提（必要なときだけ実施）:

• NEXT_PUBLIC_SENTRY_DSN and SENTRY_DSN set.
• Discord integration installed with channel ID.

推奨フィルタ（Errors -> Number of Errors, event.type:default）:

• message:"[ops] presence.degraded" level:warning
• message:"[ops] room.sync.health" level:warning
• message:"[ops] room.join.retrying" level:warning
• message:"[ops] room.access.error" level:warning
• message:"[safe-update] failure" level:warning

しきい値（初期値）:

• Critical: Above 1 for test, then raise to 3-10 per 10m window.
• Warning optional; disable or set very high.

Actions:

• Discord notification for Critical only (reduce noise).

アラート設定は docs/OPERATIONS.md に記録する。