Feat: The "inception pool" aka Ratomic::LocalPool

[kanutocd]

Summary

This PR introduces Ratomic::LocalPool, a new pooling primitive for resources that should remain local to the Ractor that created them.

Examples include:

• Redis clients
• PostgreSQL connections
• HTTP clients
• Kafka producers
• Other stateful resources with internal connection/socket/native state

Background

While experimenting with Redis clients under Ruby Ractors, the ownership-transfer semantics were exposed that they are not always appropriate for live resources.

Ratomic::Pool correctly implements ownership transfer:

Pool  -> Caller -> Pool

However, Redis clients contain internal state that cannot safely participate in ownership transfer after initialization. This resulted in failures such as:

Ractor::MovedError

Several approaches were explored, including pool reset behavior, but the underlying issue was resource ownership rather than resource cleanup.

Solution

Introduce Ratomic::LocalPool.

Instead of moving live resources between Ractors, the facade remains shareable while each Ractor lazily creates and owns its own local resource pool.

Architecture:

LocalPool facade 
       ↓
Ractor-local pool
       ↓
Live resources

Calling this the "Inception Pool" design:

Pool
  ↓
Pool
  ↓
Resource

A Pool within a Pool :)

Validation

Added Redis smoke tests covering:

basic_redis.rb

• Thread execution
• Ractor execution
• Shared facade usage

queue_redis.rb

• Multiple producers
• Multiple consumers
• Queue draining verification

Observed results:

• No Ractor::MovedError
• No Ractor::IsolationError
• Successful queue drain
• Successful operation from both Threads and Ractors