chore: updating the face and some backened

[ausbernard]

• writing/overengineering-operational-exhaustion.html — new post, May 2026, Infrastructure tag (slate-blue), full content
  rendered via marked.js, post nav links to Partida Gap
• writing/index.html — new entry at the top of the list with a two-sentence excerpt and the new tag color
• index.html — new row at the top of the homepage editorial list with the same tag
• writing/partida-gap.html — back-link added pointing to the new post so the chain is complete