Add guide method

[g-eoj]

Goal:

from cragents import CRAgent, Anchor, Constrain, Free, Think, UseTools
from pydantic_ai import ToolOutput


agent = CRAgent(model, output_type=[ToolOutput(int), ToolOutput(bool)])

generation_sequence = [
    Think(
        [
            Anchor("I think "), 
            Constrain(2,2),
            Anchor("Therefore "), 
            Free(),
        ]
    ),
    UseTools(),
]

await agent.guide(generation_sequence)

Todo:

• Tweak API
  • Handle Anchor and Block in main sequence
• Update README
• Improve test coverage
• Define stricter types