Restore `clean-repo-tabs`

[fregante]

• follows ⚠️ releases-tab, bugs-tab, clean-repo-tabs broken #8867

The tab bar is super long now due to:

• extensible-nav always showing the icons
• bugs-tab
• releases-tab

We can't bring the original feature as was because it expected a dropdown element, which we no longer have. This means we can't hide Security and Insights. What we can do:

• enable mobile-tabs earlier, like 1200px

and/or create clean-repo-tabs:

• hide Projects tab if present
• shorten Security and quality to Security
• shorten Pull requests to Pulls
• remove labels from unwanted tabs like Agents, Security, Insights

and also:

• hide the icons at middle resolutions like GitHub does natively, although I feel that this is a downgrade