🎯 refactor: Centralize Agent Model Handling Across Conversation Lifecycle (#10956)

* refactor: Implement clearModelForNonEphemeralAgent utility for improved agent handling

- Introduced clearModelForNonEphemeralAgent function to manage model state for non-ephemeral agents across various components.
- Updated ModelSelectorContext to initialize model based on agent type.
- Enhanced useNavigateToConvo, useQueryParams, and useSelectMention hooks to clear model for non-ephemeral agents.
- Refactored buildDefaultConvo and endpoints utility to ensure proper handling of agent_id and model state.
- Improved overall conversation logic and state management for better performance and reliability.

* refactor: Enhance useNewConvo hook to improve agent conversation handling

- Added logic to skip access checks for existing agent conversations, utilizing localStorage to restore conversations after refresh.
- Improved handling of default endpoints for agents based on user access and existing conversation state, ensuring more reliable conversation initialization.

* refactor: Update ChatRoute and useAuthRedirect to include user roles

- Enhanced ChatRoute to utilize user roles for improved conversation state management.
- Modified useAuthRedirect to return user roles alongside authentication status, ensuring roles are available for conditional logic in ChatRoute.
- Adjusted conversation initialization logic to depend on the loaded roles, enhancing the reliability of the conversation setup.

* refactor: Update BaseClient to handle non-ephemeral agents in conversation logic

- Added a check for non-ephemeral agents in BaseClient, modifying the exceptions set to include 'model' when applicable.
- Enhanced conversation handling to improve flexibility based on agent type.

* test: Add mock for clearModelForNonEphemeralAgent in useQueryParams tests

- Introduced a mock for clearModelForNonEphemeralAgent to enhance testing of query parameters related to non-ephemeral agents.
- This addition supports improved test coverage and ensures proper handling of model state in relevant scenarios.

* refactor: Simplify mocks in useQueryParams tests for improved clarity

- Updated the mocking strategy for utilities in useQueryParams tests to use actual implementations where possible, while still suppressing test output for the logger.
- Enhanced the mock for tQueryParamsSchema to minimize complexity and avoid unnecessary validation during tests, improving test reliability and maintainability.

* refactor: Enhance agent identification logic in BaseClient for improved clarity

* chore: Import Constants in families.ts for enhanced functionality

api/app/clients/BaseClient.js

@@ -966,6 +966,13 @@ class BaseClient {
 
     const unsetFields = {};
     const exceptions = new Set(['spec', 'iconURL']);
+    const hasNonEphemeralAgent =
+      isAgentsEndpoint(this.options.endpoint) &&
+      endpointOptions?.agent_id &&
+      endpointOptions.agent_id !== Constants.EPHEMERAL_AGENT_ID;
+    if (hasNonEphemeralAgent) {
+      exceptions.add('model');
+    }
     if (existingConvo != null) {
       this.fetchedConvo = true;
       for (const key in existingConvo) {