feat(web): shared left-sidebar navigation across all pages

Desktop nav was scattered and inconsistent — the chat header was crammed with
cross-page links and each standalone page had its own ad-hoc, incomplete back-links
(e.g. /hands could only reach Chat). Now a single nav.js (one source of truth, no
build step) injects a left sidebar on desktop (>=769px) with active-page
highlighting across Chat/Session/History/Hands/Mind/Journal/Logs + Settings.

- nav.js: injects sidebar + its own CSS; body gets padding-left on desktop; hidden
  on mobile (each page keeps its bottom bar / back-links there).
- Included on every page (index, session, history, hands, self, journal, logs,
  recap, hand).
- Decluttered the chat header: removed the now-redundant cross-page links (kept the
  chat-specific session selector + inline Live Log toggle).
- Sidebar Settings opens the chat modal, or navigates to /?settings=1 from elsewhere.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

lyra/web/static/index.html

@@ -80,11 +80,6 @@
       <button id="newSessionBtn">➕ New</button>
       <button id="renameSessionBtn">✏️ Rename</button>
       <button id="thinkingStreamBtn" title="Show live activity log">📜 Live Log</button>
-      <a id="fullLogBtn" href="/logs" target="_blank" rel="noopener" title="Open the full-page log" role="button">⛶ Full Log</a>
-      <a id="sessionBtn" href="/session" target="_blank" rel="noopener" title="Live session HUD" role="button">🎬 Session</a>
-      <a id="historyBtn" href="/history" target="_blank" rel="noopener" title="Past sessions" role="button">📚 Sessions</a>
-      <a id="mindBtn" href="/self" target="_blank" rel="noopener" title="Read her mind — Lyra's current self-state" role="button">🧠 Mind</a>
-      <a id="handsBtn" href="/hands" target="_blank" rel="noopener" title="Recorded poker hands" role="button">🃏 Hands</a>
     </div>
 
     <!-- Status -->
@@ -990,6 +985,9 @@
         loadSessionList(); // Refresh session list when opening settings
       });
 
+      // Sidebar "Settings" from another page navigates here with ?settings=1.
+      if (new URLSearchParams(location.search).get("settings")) settingsBtn.click();
+
       // Hide modal functions
       const hideModal = () => {
         settingsModal.classList.remove("show");
@@ -1187,5 +1185,6 @@
       });
     });
   </script>
+  <script src="/nav.js"></script>
 </body>
 </html>