Release 0.14.0: public /docs user guide (DOCS.md served at /docs)

Ships DOCS.md and the /docs route — a plain-prose translation of
SPEC.md for users, distinct from the binding spec. Originating need
was the admin-vs-owner role distinction on /admin/users (§6.1);
response is a single guide that covers the framework's user-facing
surfaces end-to-end (roles, proposing, branches, PRs, graduation,
notifications). Mirrors /philosophy: markdown file at repo root +
sibling backend loader + MarkdownPreview render. No schema migration.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

frontend/src/api.js

@@ -632,6 +632,10 @@ export async function getPhilosophy() {
   return jsonOrThrow(await fetch('/api/philosophy'))
 }
 
+export async function getDocs() {
+  return jsonOrThrow(await fetch('/api/docs'))
+}
+
 // ---------------------------------------------------------------------------
 // Slice 7: admin neighborhood (§17 admin/* + user search for the §15.8 mute
 // typeahead).