Write a SpacetimeDB backend module in TypeScript that defines an event table for damage notifications and a reducer that publishes events to it.

TABLES
- damageEvent
  - public event table (rows exist only for the duration of the transaction, set event: true)
  - Fields:
    - entityId: number (u64)
    - damage: number (u32)
    - source: string

REDUCERS
- deal_damage(ctx, { entityId: number (u64), damage: number (u32), source: string })
  - Insert a row into the damageEvent event table
