🤔 Problem Description

The current naming of agent set classes is confusing for new users:

• AgentSetDF is actually an abstract class, but its name suggests it is concrete.
• AgentSetPolars is the concrete implementation, but its name suggests a backend-specific detail rather than the default user-facing API.
• Similarly, AgentContainer is an abstract base but does not indicate this in its name.

This inconsistency makes it harder for users (especially newcomers) to understand the intended API.

💡 Proposed Solution

• Rename AgentSetDF → AbstractAgentSetDF
• Rename AgentSetPolars → AgentSetDF
• Optionally Rename AgentContainer → AbstractAgentContainer for consistency

This way, abstract vs. concrete roles are explicit and easier to follow.

🔄 Alternatives Considered

No response

➕ Additional Context

• This will be a breaking change since imports will need updating.
• We should implement this before publishing 0.1.0 stable, to avoid renaming pain for users later.