Refactor site generation into a modular content pipeline

clean.js

@@ -1,3 +1,4 @@
 import { rm } from 'node:fs/promises'
+import { generatedRoot } from './site.config.js'
 
-await Promise.all([rm('.generated', { recursive: true, force: true }), rm('dist', { recursive: true, force: true })])
+await Promise.all([rm(generatedRoot, { recursive: true, force: true }), rm('dist', { recursive: true, force: true })])