feat(06-01): add Nitro hook content:file:afterParse for reading-time injection

- Register `content:file:afterParse` hook to inject `wordCount` + `minutes`
  on every parsed markdown content object (D-19: 200 wpm, floor 1 min).
- Import pure util `countWordsInMinimalBody` from app/utils/countWords.
- Guard against non-`.md` files (defensive — hook fires on all sources).
- Values persist in @nuxt/content SQLite DB and are queryable via
  queryCollection thanks to matching Zod fields (content.config.ts).

server/plugins/reading-time.ts

@@ -0,0 +1,23 @@
+import { countWordsInMinimalBody } from '~/utils/countWords'
+
+/**
+ * Nitro plugin: compute reading time for every markdown content file at parse time.
+ *
+ * Injects `wordCount` (number) and `minutes` (number, min 1) on the content object.
+ * Values are persisted in the @nuxt/content SQLite DB and queryable via queryCollection
+ * thanks to the matching Zod schema fields in content.config.ts (per D-18 + D-19).
+ *
+ * Hook reference: https://content.nuxt.com/docs/advanced/hooks
+ */
+export default defineNitroPlugin((nitroApp) => {
+  nitroApp.hooks.hook('content:file:afterParse', (ctx) => {
+    const { file, content } = ctx
+
+    // Only process markdown files (defensive — hook fires on all sources)
+    if (!file.id?.endsWith('.md')) return
+
+    const wordCount = countWordsInMinimalBody(content.body)
+    content.wordCount = wordCount
+    content.minutes = Math.max(1, Math.ceil(wordCount / 200)) // D-19: 200 wpm, floor 1 min
+  })
+})