Fix lint errors and bump golangci-lint to v2/action v9

- Migrate .golangci.yml to golangci-lint v2 config format
- Bump golangci-lint-action from v6 (Node 20, deprecated) to v9 (Node 24)
- Fix errcheck: check fmt.Fscanln and fmt.Sscanf return values
- Fix ineffassign: replace unused vars with _ in test files
- Fix revive unused-parameter: rename unused cmd/args/r/c params to _
- Fix revive empty-block: invert if condition in push command
- Fix revive redefines-builtin-id: rename 'clear' to 'clearsigned'
- Fix revive blank-imports: add comment on modernc.org/sqlite import
- Fix unused: remove unused 'suite' and 'gen' fields from cache entry

cli/commands/version.go

@@ -10,7 +10,7 @@ func (r *Root) versionCmd() *cobra.Command {
 	return &cobra.Command{
 		Use:   "version",
 		Short: "Print the urapt CLI version",
-		Run: func(cmd *cobra.Command, args []string) {
+		Run: func(_ *cobra.Command, _ []string) {
 			fmt.Println(r.version)
 		},
 	}