Disabling manual update of r shiny sliderinput and only allowing updatesliderinput to change it

I shamelessly copied this example of co-dependent R Shiny sliderInput from another answer on this forum. I want this behavior with a minor twist. I want one of the sliders to NOT allow user input, but only update and slide when the OTHER slider is changed.

Is there a way to do that? Additionally, I want to "MARK" the initial value on both sliders so the user knows how they changed the slider from the INITIAL value.

library(shiny)

ui =pageWithSidebar(
  headerPanel("Glass fullness"),
  sidebarPanel(
    sliderInput(inputId = "Full", label = "% water", min = 0, max = 1, value = 0.2),
    sliderInput(inputId = "Empty", label = "% air", min = 0, max = 1, value = 1 - 0.2),
    uiOutput("Empty")),
  mainPanel()
)

server = function(input, output, session){
  
  # when water change, update air
  observeEvent(input$Full,  {
    updateSliderInput(session = session, inputId = "Empty", value = 1 - input$Full)
  })
  
  # when air change, update water
  observeEvent(input$Empty,  {
    updateSliderInput(session = session, inputId = "Full", value = 1 - input$Empty)
  })
  
}

shinyApp(ui = ui, server = server)

You may disable the other input (used shinyjs::disabled) and I have used the label of sliderInput to mark the initial value.

library(shiny)
library(shinyjs)

initial_water <- 0.2
initial_air <- 1 - initial_water

ui = pageWithSidebar(
  headerPanel("Glass fullness"),
  sidebarPanel(
    useShinyjs(),
    sliderInput(inputId = "Full", 
                label = paste('% water (initial value : ', initial_water, ')'), 
                min = 0, max = 1, value = initial_water),
    shinyjs::disabled(
      sliderInput(inputId = "Empty", 
                  label = paste('% water (initial value : ', initial_air, ')'), 
                  min = 0, max = 1, value = initial_air)
    ),
    uiOutput("Empty")),
  mainPanel()
)

server = function(input, output, session){
  
  # when water change, update air
  observeEvent(input$Full,  {
    updateSliderInput(session = session, inputId = "Empty", value = 1 - input$Full)
  })
  
}

shinyApp(ui = ui, server = server)