Validate request queue input before sending it #1093

The request queue methods accept input that the API or the JS client rejects:

• add_request() and batch_add_requests() take RequestWithoutId, which has extra='allow' (_models.py:2847-2853), so a request that carries an id is sent to the API as is. The JS client rejects a request with an id before sending it.
• batch_delete_requests() doesn't check the item count (_resource_clients/request_queue.py:493-529). The API accepts 1 to 25 requests, and the JS client validates that range.
• batch_add_requests() accepts an empty list. The JS client rejects it.

Validate these on the client side and raise a ValueError. Code that passes such input today would start failing, so this goes into a major.

✍️ Drafted by Claude Code