news: track @newsHidden in Caddy snapshot + extract testable feed routing helpers

Housekeeping per Codex:
- Mirror the live @newsHidden rule into deploy/caddy/Caddyfile.snapshot so the
  /news noindex protection is reproducibly recorded.
- Extract the feed's routing helpers (feedBase/parseView/viewUrl) into pure
  $lib/feednav.js and unit-test them (the base-aware URL generation wasn't
  exercised by the prior suite). NewsFeed imports them; behavior unchanged.

(Note: the step-1 commit also swept in data/wotd_audio/renewal.mp3 — a legit
cached pronunciation, not extraction-related; left as-is per Codex.)

32 frontend tests green; build clean.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

deploy/caddy/Caddyfile.snapshot

@@ -63,6 +63,12 @@ upbeatbytes.com {
 		header @hidden X-Robots-Tag "noindex, nofollow"
 
 		# /news is the feed's future home — rendered during the relaunch transition but kept
+		# noindex (FOLLOW, so link equity still flows) until cutover, when this line is removed
+		# and /news enters the sitemap. Avoids publishing a duplicate indexable feed.
+		@newsHidden path /news /news.html
+		header @newsHidden X-Robots-Tag "noindex, follow"
+
+		# Content-hashed assets never change for a given URL — cache them forever.
 		@immutable path /_app/immutable/*
 		header @immutable Cache-Control "public, max-age=31536000, immutable"