Support multiple agents in the same database

[gregsaab]

At present, this is only supporting one agent per db instance as the schema agent is hardcoded. To support multi-agent environments, we should support multiple agents within a single db instance.

To accomplish this, we'd need to:

• add an agent-id field to the events table
• add an explicit id field onto the TigerAgent class (or onto the EventHarness object), but use BOT_TOKEN as backup
• update claim_event() and _insert_event() to specify the relevent id

See thread: https://iobeam.slack.com/archives/C09AF06P37B/p1758811756337849