Add series support and publish "ai didn't break the laws of physics"

[rdavid1099]

Problem

The build pipeline had no way to express ordered multi-part series. Posts inside a theme folder all sorted newest-first with no concept of reading order, and there was no mechanism for a theme to surface a human-readable series title or per-post part numbers.

Solution

Extended build.js to recognize a theme folder as a "series" when every post in it declares an integer part frontmatter field. Series themes sort ascending by part number instead of descending by date, use the series frontmatter string as their section heading on the homepage and listing page, and render a small "Part N" kicker above each post title in every listing context. A helper isSeriesPosts drives all of this so the logic stays in one place. The homepage sort also promotes series sections above regular topic buckets so a curated reading path sits above unordered tag groupings.

Added a .post-part CSS rule to render the kicker as a small, muted, uppercase label that sits cleanly above the post title without competing with it.

With the infrastructure in place, published the first post in the "understanding clients in the age of ai" series: "ai didn't break the laws of physics," which covers the Entity Knowledge Base Engine rebuild at Table22, the scope-cutting discipline that made it shippable in a week, and why de-risking in throwaway prototypes was the real prerequisite for committing to permanent architecture.

Notes

The series heading on the listing page and homepage is pulled from posts[0].series, so all posts in a series folder must carry the same series value. A mismatch won't error today; it will silently use whatever the first (lowest part number) post declares.