fix: prevent secret variable leaks in summary, verbose and key ordering

- mask secret values in `task --summary` (commands and vars listing)
- mask resolved value of dynamic (sh) secrets in verbose logs
- use masked command for platform-skipped verbose log
- allow `secret` key in any position in a var definition (not only first)
- add `value` to the JSON schema var definition
- skip masking pass when no secret is present and dedup mask helpers
- document that the `secret` flag is not propagated to derived variables

task.go

@@ -390,7 +390,7 @@ func (e *Executor) runCommand(ctx context.Context, t *ast.Task, call *Call, i in
 		return err
 	case cmd.Cmd != "":
 		if !shouldRunOnCurrentPlatform(cmd.Platforms) {
-			e.Logger.VerboseOutf(logger.Yellow, "task: [%s] %s not for current platform - ignored\n", t.Name(), cmd.Cmd)
+			e.Logger.VerboseOutf(logger.Yellow, "task: [%s] %s not for current platform - ignored\n", t.Name(), cmd.LogCmd)
 			return nil
 		}