# Remove action_type from Kafka Payload

## Context
User requested to ensure `action_type` is determined solely by the backend logic and is NOT accepted from the Kafka payload.

## Changes
1.  **Documentation**:
    - Updated `docs/kafka_format.md` to remove `action_type` from the input schema and examples.
2.  **Schema Validation**:
    - Updated `src/schema/kafkaPayload.js` to remove `action_type` from the Zod schema.
3.  **Processor Logic**:
    - Confirmed `src/processor/index.js` already independently calculates `action_type` using `resolveActionType` (based on `direction` and `cmd_word`).
    - The code does not use any `action_type` from the payload, ensuring strict adherence to the new rule.

## Verification
- Unit tests (`tests/processor.test.js`) pass successfully.
- The system now ignores any `action_type` field if it were to be sent (schema validation would strip it if `strict` mode was on, but default Zod `parse` strips unknown keys unless `passthrough` is used. Wait, Zod default behavior strips unknown keys).
- Actually, Zod by default *strips* unknown keys. So if `action_type` is sent but not in schema, it will be removed. Perfect.
