Token Budget Allocator

Design a token budget allocation system for complex multi-step pipelines.

## Pipeline Steps
{{pipeline_steps}}

## Total Budget
{{total_token_budget}}

## Priority Rules
{{priority_rules}}

Implement allocation:

```python
class TokenBudgetAllocator:
    def __init__(self, total_budget: int, steps: List[PipelineStep]):
        pass
    
    def allocate(self, content_lengths: Dict[str, int]) -> Dict[str, int]:
        """
        Allocation strategies:
        - Fixed allocation per step
        - Dynamic based on content
        - Priority-based with minimums
        """
        pass
    
    def rebalance(self, used: Dict[str, int], remaining_steps: List[str]) -> Dict[str, int]:
        """Rebalance unused tokens to later steps"""
        pass
    
    def enforce_budget(self, step: str, content: str, budget: int) -> str:
        """Truncate/summarize to fit budget"""
        pass
```

Include:
- Dynamic rebalancing
- Priority handling
- Overflow strategies
- Budget tracking metrics