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/tools/search.go

@@ -39,7 +39,7 @@ func NewSearchTool(db *store.DB, provider ai.Provider, search config.SearchConfi
 func (t *SearchTool) Handle(ctx context.Context, req *mcp.CallToolRequest, in SearchInput) (*mcp.CallToolResult, SearchOutput, error) {
 	query := strings.TrimSpace(in.Query)
 	if query == "" {
-		return nil, SearchOutput{}, errInvalidInput("query is required")
+		return nil, SearchOutput{}, errRequiredField("query")
 	}
 
 	limit := normalizeLimit(in.Limit, t.search)