fix(runtime): surface unresolved action targets instead of dropping silently

serializeAction emitted {x:0,y:0} via `?? 0` whenever a Tap/InputText/Swipe
target failed to resolve to coordinates. The runner then collapsed those
to ErrNoAction, so every selector typo became a silent no-op tick.

Have the runtime return null on unresolved targets and log a console
warning (visible via chromedp's runtime listener). Drop the now-redundant
{0,0} -> ErrNoAction guard so a deliberate Tap at the origin actually
fires.

internal/runner/runner.go

@@ -446,9 +446,6 @@ func nextActionFromV8(ctx context.Context, web driver.WebDriver) (verifier.Actio
 	}
 	switch decoded.Kind {
 	case "Tap":
-		if decoded.X == 0 && decoded.Y == 0 {
-			return verifier.Action{}, verifier.ErrNoAction
-		}
 		return verifier.Action{Kind: verifier.ActionKindTap, X: decoded.X, Y: decoded.Y}, nil
 	case "InputText":
 		return verifier.Action{