Per environment or per stack overrides for ai allowed and blocked tools settings

### Describe the Feature

I was reading through https://atmos.tools/cli/configuration/ai/tools and setting up the AI following the best practices section.

```yaml
ai:
tools:
enabled: true
allowed_tools: [] # Prompt for everything
blocked_tools:
- execute_* # Block all execution tools
- write_* # Block all write operations

# Development: more permissive
ai:
tools:
enabled: true
allowed_tools:
- atmos_describe_* # Auto-approve read-only
- atmos_list_*
- atmos_validate_*
blocked_tools:
- execute_bash_command # Block shell execution
```

We have our repo structured:
```
components/
terraform/
stacks/
azure/
/
/
.yaml
```

We'd like to configure the lowest environments so that ai has full permissions there but read only in dev and higher.

### Expected Behavior

Able to configure allowed and blocked tools for ai on each stack and environment independently from other stacks or environments, which override the defaults from atmos.yaml entirely.

### Use Case

_No response_

### Describe Ideal Solution

_No response_

### Alternatives Considered

_No response_

### Additional Context

_No response_