Release v0.20.0: /docs/specs surface + nested flyout nav + session body-list removal

Wave 9 follow-up to roadmap item #30 (Session 0017.0 shipped #30 as v0.19.0;
v0.20.0 lands the operator-feedback follow-ups on top).

1. Specs on /docs/specs/<name> (backend docs_specs.py + frontend DocsSpec.jsx
   + DocsSpecsIndex.jsx). Configured via OHM_DOCS_SPECS; framework default
   carries OHM's two specs (rfc-app/SPEC.md + flotilla SPEC.md). Runtime
   fetch from gitea raw with 5-min TTL cache, mirroring docs_sessions.py.

2. Nested flyout nav hierarchy (DocsLayout.jsx). Sessions render as a tree
   with transcripts nested under each session row (labeled by .N ordinal).
   New Specs section between User Guide and Sessions.

3. /docs/sessions/<NNNN> body-list removed (DocsSessionIndex.jsx). Body
   becomes a session-overview card; navigation lives in the left nav.

19 new pytest cases for docs_specs (332 backend total green). Frontend
build clean. Sync frontend/package-lock.json version drift (0.15.0 → 0.20.0)
alongside the VERSION + package.json bump.

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

frontend/src/App.jsx

@@ -17,6 +17,8 @@ import DocsUserGuide from './components/DocsUserGuide.jsx'
 import DocsSessionsAbout from './components/DocsSessionsAbout.jsx'
 import DocsSessionIndex from './components/DocsSessionIndex.jsx'
 import DocsSessionTranscript from './components/DocsSessionTranscript.jsx'
+import DocsSpec from './components/DocsSpec.jsx'
+import DocsSpecsIndex from './components/DocsSpecsIndex.jsx'
 import NotificationSettings from './components/NotificationSettings.jsx'
 import Admin from './components/Admin.jsx'
 import AcceptInvitation from './components/AcceptInvitation.jsx'
@@ -329,6 +331,11 @@ function DocsWithSidebar({ viewer }) {
           <Route path="sessions/about" element={<DocsSessionsAbout />} />
           <Route path="sessions/:nnnn" element={<DocsSessionIndex />} />
           <Route path="sessions/:nnnn/:filename" element={<DocsSessionTranscript />} />
+          {/* v0.20.0 — /docs/specs/* surface (framework spec + flotilla spec
+              at runtime via gitea raw). Bare /docs/specs lands on the
+              client-side redirect to the first configured spec. */}
+          <Route path="specs" element={<DocsSpecsIndex />} />
+          <Route path="specs/:name" element={<DocsSpec />} />
         </Route>
       </Routes>
     </main>