Spawn a generic BEAM child process under the agent's supervisor.

This is a low-level, fire-and-forget directive for spawning non-agent processes (Tasks, GenServers, etc.). The spawned process is not tracked in the agent's children map and has no parent-child relationship semantics.

Use SpawnAgent instead if you need to spawn another Jido agent with:

• Parent-child hierarchy tracking
• Process monitoring and exit signals
• The ability to use emit_to_parent/3 from the child
• Lifecycle management via StopChild

Fields

• child_spec - Supervisor child_spec for the process to spawn
• tag - Optional correlation tag for logging (not used for tracking)