Update README for repo archiving

Co-authored-by: Christopher Bull <5499680+chrisb13@users.noreply.github.com>

Author: dougiesquire

README.md

@@ -1,19 +1,12 @@
 <img src="https://github.com/COSIMA/logo/blob/master/png/logo_word.png" width="300"/>&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<img src="https://www.access-nri.org.au/wp-content/themes/accessnri/images/logos/access_logo_rgb.svg" width="200"/>
-<br/> <br/>
-[![Compilation Status](https://github.com/COSIMA/access-om3/actions/workflows/compilation.yml/badge.svg)](https://github.com/COSIMA/access-om3/actions/workflows/compilation.yml)
 
-This repository is **deprecated**!
+> [!IMPORTANT]
+> **This repository has been deprecated and is read-only**
 
 # ACCESS-OM3
 
 ACCESS-OM3 is a global coupled ocean - sea ice - wave model being developed by [COSIMA](http://www.cosima.org.au) and [ACCESS-NRI](https://www.access-nri.org.au/). It consists of MOM6, CICE6 and (optionally) WaveWatch3, coupled with NUOPC and driven by prescribed surface forcing - see [here](https://access-om3-configs.access-hive.org.au/pages/Architecture/).
 
-# Downloading
-
-This repository only stores (no longer used!) model source code and is **deprecated**. **This repo is only useful to users wanting to browse *older* builds of ACCESS-OM3**.
+This repository only stores (no longer used!) model source code and is **deprecated**. **This repo is only useful to users wanting to browse *old* builds of ACCESS-OM3**.
 
 Model configurations are available from branches in [github.com/ACCESS-NRI/access-om3-configs](https://github.com/ACCESS-NRI/access-om3-configs), which use pre-built executables available on [NCI](https://nci.org.au/). Whilst it is not needed to run the model, the newer build system uses Spack and is [here](https://github.com/aCCESS-NRI/acceSS-OM3). NCI-based users of ACCESS-OM3 typically won't need to download the build repository unless they need to make model component code changes.
-
-# Documentation (including building and running the model)
-
-See [access-om3-configs.access-hive.org.au](https://access-om3-configs.access-hive.org.au/), particularly the [quick start](https://access-om3-configs.access-hive.org.au/pages/Quick-start/).