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>

frontend/src/lib/feednav.js

@@ -0,0 +1,28 @@
+// Pure routing helpers for the news feed, shared by its two mounts: `/` (interim,
+// becomes the hub at cutover) and `/news` (its permanent home). Kept framework-free
+// so they're unit-testable without mounting the Svelte component.
+
+// Which base path the feed is rendering at. `/news` is permanent; `/` is the interim
+// mount. Anything not under /news is treated as `/`.
+export function feedBase(pathname) {
+  return (pathname || '').startsWith('/news') ? '/news' : '/';
+}
+
+// The current view key, derived from query params only (path-agnostic, so a deep link
+// works at either base): search > source > tag > explicit view > 'today' (Highlights).
+export function parseView(url) {
+  const p = url.searchParams;
+  if ((p.get('q') || '').trim()) return 'search';
+  if (p.get('source')) return 'source:' + p.get('source');
+  if (p.get('tag')) return 'tag:' + p.get('tag');
+  return p.get('view') || 'today';
+}
+
+// A link to a view at the given base path. 'today' is the bare base; everything else
+// carries its query param so the same parseView() reads it back identically.
+export function viewUrl(base, key) {
+  if (key === 'today') return base;
+  if (key.startsWith('source:')) return base + '?source=' + encodeURIComponent(key.slice(7));
+  if (key.startsWith('tag:')) return base + '?tag=' + encodeURIComponent(key.slice(4));
+  return base + '?view=' + encodeURIComponent(key);
+}