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/mcperrors/mcperrors.go

@@ -0,0 +1,30 @@
+package mcperrors
+
+const (
+	CodeSessionRequired = -32050
+	CodeProjectRequired = -32051
+	CodeProjectNotFound = -32052
+	CodeInvalidID       = -32053
+	CodeEntityNotFound  = -32054
+)
+
+const (
+	TypeInvalidArguments = "invalid_arguments"
+	TypeInvalidInput     = "invalid_input"
+	TypeSessionRequired  = "session_required"
+	TypeProjectRequired  = "project_required"
+	TypeProjectNotFound  = "project_not_found"
+	TypeInvalidID        = "invalid_id"
+	TypeEntityNotFound   = "entity_not_found"
+)
+
+type Data struct {
+	Type    string   `json:"type"`
+	Field   string   `json:"field,omitempty"`
+	Fields  []string `json:"fields,omitempty"`
+	Value   string   `json:"value,omitempty"`
+	Detail  string   `json:"detail,omitempty"`
+	Hint    string   `json:"hint,omitempty"`
+	Project string   `json:"project,omitempty"`
+	Entity  string   `json:"entity,omitempty"`
+}