feat(web): bottom tab bar navigation (M4)

- Mobile bottom tab bar: Chat · Hands · Mind · More. "More" opens the drawer
  for the long tail (Journal, Log, Settings, sessions); hamburger retired.
- Auto-hides while the keyboard is open (body.kb) so the input pins to the
  keyboard; mobile-only (desktop keeps its header nav).
- Removed now-redundant Mind/Hands from the drawer + their listeners.
- Bottom-fill fix: #chat uses 100dvh (the visible viewport) — 100vh/inset:0
  reach into the home-indicator zone iOS won't comfortably show, clipping the
  bar; dvh/svh exclude it. Tab bar is flex:none with a small fixed bottom
  padding (safe-area padding double-counts at dvh height), and the body bg
  matches the bar so any strip below #chat is seamless.

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

lyra/web/static/index.html

@@ -41,9 +41,7 @@
       <h4>Actions</h4>
       <button id="mobileThinkingStreamBtn">📜 Live Log (inline)</button>
       <button id="mobileFullLogBtn">⛶ Full Log</button>
-      <button id="mobileMindBtn">🧠 Read Her Mind</button>
       <button id="mobileJournalBtn">📔 Journal</button>
-      <button id="mobileHandsBtn">🃏 Hands</button>
       <button id="mobileSettingsBtn">⚙ Settings</button>
       <button id="mobileToggleThemeBtn">🌙 Toggle Theme</button>
       <button id="mobileForceReloadBtn">🔄 Force Reload</button>
@@ -116,6 +114,14 @@
       <input id="userInput" type="text" placeholder="Type a message..." autofocus />
       <button id="sendBtn">Send</button>
     </div>
+
+    <!-- Bottom tab bar (mobile only; hides while the keyboard is open) -->
+    <nav id="tabbar" aria-label="Primary navigation">
+      <a class="tab active" href="/" aria-current="page"><span class="ti">💬</span><span class="tl">Chat</span></a>
+      <a class="tab" href="/hands"><span class="ti">🃏</span><span class="tl">Hands</span></a>
+      <a class="tab" href="/self"><span class="ti">🧠</span><span class="tl">Mind</span></a>
+      <button class="tab" id="moreTab" type="button"><span class="ti">⋯</span><span class="tl">More</span></button>
+    </nav>
   </div>
 
   <!-- Settings Modal (outside chat container) -->
@@ -523,6 +529,8 @@
         // iOS pans the visual viewport when the keyboard opens; follow its top
         // edge so the pinned #chat sits exactly in the visible area.
         root.setProperty("--app-offset", off + "px");
+        // Keyboard open ⇒ hide the bottom tab bar so the input pins to the keyboard.
+        document.body.classList.toggle("kb", (window.innerHeight - h) > 150);
       }
       // Re-measure across the keyboard animation: iOS reports a stale (too-short)
       // height mid-animation, so sample a few times until it settles.
@@ -568,6 +576,7 @@
 
       hamburgerMenu.addEventListener("click", toggleMobileMenu);
       mobileMenuOverlay.addEventListener("click", closeMobileMenu);
+      document.getElementById("moreTab").addEventListener("click", toggleMobileMenu);
 
       // Sync mobile menu controls with desktop
       const mobileMode = document.getElementById("mobileMode");
@@ -1011,15 +1020,9 @@
       document.getElementById("mobileFullLogBtn").addEventListener("click", () => {
         closeMobileMenu(); window.location.href = "/logs";
       });
-      document.getElementById("mobileMindBtn").addEventListener("click", () => {
-        closeMobileMenu(); window.location.href = "/self";
-      });
       document.getElementById("mobileJournalBtn").addEventListener("click", () => {
         closeMobileMenu(); window.location.href = "/journal";
       });
-      document.getElementById("mobileHandsBtn").addEventListener("click", () => {
-        closeMobileMenu(); window.location.href = "/hands";
-      });
 
       // Connect to the global live log on page load.
       connectThinkingStream();