test(tools): add unit tests for error handling functions

* Implement tests for error functions like errRequiredField, errInvalidField, and errEntityNotFound.
* Ensure proper metadata is returned for various error scenarios.
* Validate error handling in CRM, Files, and other tools.
* Introduce tests for parsing stored file IDs and UUIDs.
* Enhance coverage for helper functions related to project resolution and session management.

internal/config/validate.go

@@ -33,6 +33,9 @@ func (c Config) Validate() error {
 	if strings.TrimSpace(c.MCP.Path) == "" {
 		return fmt.Errorf("invalid config: mcp.path is required")
 	}
+	if c.MCP.SessionTimeout <= 0 {
+		return fmt.Errorf("invalid config: mcp.session_timeout must be greater than zero")
+	}
 
 	switch c.AI.Provider {
 	case "litellm", "ollama", "openrouter":