Fixes Ubuntu misidentifying .pub SSH public keys as Microsoft Publisher files (application/x-mspublisher)

ssh-public-key.xml

<?xml version="1.0" encoding="UTF-8"?>
<!--
  =============================================================================
  HOW TO INSTALL (Local User Only):
  1. Save this file:
     Command: mkdir -p ~/.local/share/mime/packages
              nano ~/.local/share/mime/packages/ssh-public-key.xml
  
  2. Update the system MIME database:
     Command: update-mime-database ~/.local/share/mime

  =============================================================================
  HOW TO INSTALL SYSTEM-WIDE (All Users):
  1. Save this file to: /usr/share/mime/packages/ssh-public-key.xml
  2. Update the global database: sudo update-mime-database /usr/share/mime
-->
<mime-info xmlns="freedesktop.org">
  <mime-type type="application/ssh-public-key">
    <comment>SSH Public Key</comment>
    
    <!-- Priority 60 forces content sniffing to override the default *.pub extension rule -->
    <magic priority="60">
      <!-- Standard OpenSSH Key Prefixes -->
      <match type="string" offset="0" value="ssh-rsa"/>
      <match type="string" offset="0" value="ssh-ed25519"/>
      <match type="string" offset="0" value="ecdsa-sha2-"/>
      <match type="string" offset="0" value="ssh-dss"/>
      
      <!-- FIDO2 Hardware Key Prefixes -->
      <match type="string" offset="0" value="sk-ssh-ed25519@openssh.com"/>
      <match type="string" offset="0" value="sk-ecdsa-sha2-nistp256@openssh.com"/>
      
      <!-- RFC 4716 Commercial SSH Key Prefix -->
      <match type="string" offset="0" value="---- BEGIN SSH2 PUBLIC KEY ----"/>
    </magic>
    
    <glob pattern="*.pub"/>
  </mime-type>
</mime-info>