Fix reading time units

Fix time to read is marked done, but no page on production shows a reading time. The pipeline has a unit mismatch:

• PageMeta.readingTime is documented as "override in minutes"
• getPageInfo() returns size: meta.readingTime ?? 0
• ReadingTime.svelte computes Math.ceil(info.size / 200), treating it as words, and hides itself when size is 0 — which it always is, because no page sets readingTime
• renderBlogPage() computes a real wordCount via cheerio, but it only reaches the feed, not info

Tasks

• Decide the unit: expose info.wordCount (from the renderer) and info.readingTime (minutes, override or derived)
• Render minutes directly in ReadingTime.svelte
• Intl.DurationFormat is only Baseline 2025; add a plain fallback string for older engines
• Add a unit test for the minutes calculation