Implement lazy initialization for agent components

[harish0101-ops]

lazy initialization tools_impl in SwarmsAgentBuilder

pub struct SwarmsAgentBuilder<M>
where
    M: llm::Model + Send + Sync,
    M::RawCompletionResponse: Send + Sync,
{
    /// The LLM model instance used for generating responses
    model: M,
    /// Agent configuration including execution parameters
    config: AgentConfig,
    /// Optional system prompt to guide agent behavior
    system_prompt: Option<String>,
    /// List of tool definitions available to the agent
    tools: Vec<ToolDefinition>,
    /// Implementation instances of tools, keyed by tool name
    tools_impl: OnceLock<DashMap<String, Arc<dyn ToolDyn>>>,
}

plus short_memory and tools_impl in SwarmsAgent

#[derive(Clone, Serialize)]
pub struct SwarmsAgent<M>
where
    M: llm::Model + Clone + Send + Sync,
    M::RawCompletionResponse: Clone + Send + Sync,
{
    /// The LLM model used for generating responses
    model: M,
    /// Agent configuration including execution parameters
    config: AgentConfig,
    /// Optional system prompt that guides agent behavior
    system_prompt: Option<String>,
    /// Short-term memory for maintaining conversation history
    #[serde(skip)]
    short_memory: OnceLock<AgentShortMemory>,
    /// List of available tool definitions
    tools: Vec<ToolDefinition>,
    /// Tool implementation instances (not serialized)
    #[serde(skip)]
    tools_impl: OnceLock<DashMap<String, Arc<dyn ToolDyn>>>,
}

other files changes because of cargo fmt changes

Fixes #50

[kyegomez]

@harish0101-ops hey there are some merge conflicts we need to fix here!

[harish0101-ops]

@harish0101-ops hey there are some merge conflicts we need to fix here!

Done