[model-gateway] fix imports and delete unused code (#14911)

sgl-model-gateway/src/core/workflow/steps/mcp_registration.rs

@@ -97,8 +97,6 @@ pub struct DiscoverMcpInventoryStep;
 #[async_trait]
 impl StepExecutor for DiscoverMcpInventoryStep {
     async fn execute(&self, context: &mut WorkflowContext) -> WorkflowResult<StepResult> {
-        use rmcp::{service::RunningService, RoleClient};
-
         let config_request: Arc<McpServerConfigRequest> =
             context.get_or_err("mcp_server_config")?;
         let app_context: Arc<AppContext> = context.get_or_err("app_context")?;
@@ -143,8 +141,6 @@ pub struct RegisterMcpServerStep;
 #[async_trait]
 impl StepExecutor for RegisterMcpServerStep {
     async fn execute(&self, context: &mut WorkflowContext) -> WorkflowResult<StepResult> {
-        use rmcp::{service::RunningService, RoleClient};
-
         let config_request: Arc<McpServerConfigRequest> =
             context.get_or_err("mcp_server_config")?;
         let app_context: Arc<AppContext> = context.get_or_err("app_context")?;

sgl-model-gateway/src/core/workflow/steps/worker_removal.rs

@@ -9,7 +9,7 @@
 //! 3. RemoveFromWorkerRegistry - Remove workers from worker registry
 //! 4. UpdateRemainingPolicies - Update cache-aware policies for remaining workers
 
-use std::{collections::HashSet, sync::Arc};
+use std::{collections::HashSet, sync::Arc, time::Duration};
 
 use async_trait::async_trait;
 use tracing::{debug, info};
@@ -239,8 +239,6 @@ impl StepExecutor for UpdateRemainingPoliciesStep {
 
 /// Create a worker removal workflow definition
 pub fn create_worker_removal_workflow() -> WorkflowDefinition {
-    use std::time::Duration;
-
     WorkflowDefinition::new("worker_removal", "Remove worker from router")
         .add_step(
             StepDefinition::new(

sgl-model-gateway/src/core/workflow/types.rs

@@ -269,9 +269,6 @@ pub enum WorkflowError {
 
     #[error("Context value not found: {0}")]
     ContextValueNotFound(String),
-
-    #[error("Context value type mismatch: {0}")]
-    ContextTypeMismatch(String),
 }
 
 pub type WorkflowResult<T> = Result<T, WorkflowError>;