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_test.go

@@ -1,11 +1,14 @@
 package config
 
-import "testing"
+import (
+	"testing"
+	"time"
+)
 
 func validConfig() Config {
 	return Config{
 		Server: ServerConfig{Port: 8080},
-		MCP:    MCPConfig{Path: "/mcp"},
+		MCP:    MCPConfig{Path: "/mcp", SessionTimeout: 10 * time.Minute},
 		Auth: AuthConfig{
 			Keys: []APIKey{{ID: "test", Value: "secret"}},
 		},
@@ -121,3 +124,12 @@ func TestValidateRejectsInvalidMetadataRetryConfig(t *testing.T) {
 		t.Fatal("Validate() error = nil, want error for invalid metadata retry config")
 	}
 }
+
+func TestValidateRejectsInvalidMCPSessionTimeout(t *testing.T) {
+	cfg := validConfig()
+	cfg.MCP.SessionTimeout = 0
+
+	if err := cfg.Validate(); err == nil {
+		t.Fatal("Validate() error = nil, want error for invalid mcp session timeout")
+	}
+}