jbot: anchor voice button to bottom via unified right-footer

- Merged hint text + VoiceButton into a single .right-footer div
  (flex column, white bg, border-top) so they form one solid footer bar
  visually anchored to the bottom of the right column — no more floating
- .right-col gets min-height:0 so flex children can shrink properly
- .vbtn-wrap is now a transparent width:100% wrapper inside right-footer
  (desktop); mobile keeps its own fixed-position overlay
- .right-footer { display: none } on mobile (fixed vbtn-wrap takes over)

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

static_src/jbot/App.css

@@ -105,6 +105,7 @@
 .right-col {
   flex: 1;
   min-width: 0;
+  min-height: 0;
   display: flex;
   flex-direction: column;
   overflow: hidden;
@@ -599,21 +600,27 @@ kbd {
   /* Chat padding tighter on mobile */
   .chat-panel { padding: 10px 12px; }
 
-  /* Right hint hidden on mobile — space is tight */
-  .right-hint { display: none; }
+  /* On mobile the footer is replaced by the fixed vbtn-wrap */
+  .right-footer { display: none; }
 }
 
 
 /* ── Right column hint bar ────────────────────────────────── */
-.right-hint {
+.right-footer {
   flex: 0 0 auto;
+  display: flex;
+  flex-direction: column;
+  align-items: center;
+  gap: 6px;
+  padding: 8px 16px 14px;
+  background: var(--surface);
+  border-top: 1px solid var(--border);
+}
+.right-hint {
   font-size: 0.72rem;
   color: var(--text3);
   text-align: center;
-  padding: 3px 16px 2px;
   line-height: 1.7;
-  border-top: 1px solid var(--border);
-  background: var(--surface);
 }
 
 
@@ -923,12 +930,9 @@ kbd {
 
 /* ── Hold-to-talk voice button ────────────────────────────── */
 .vbtn-wrap {
-  flex: 0 0 auto;
+  width: 100%;
   display: flex;
   justify-content: center;
-  padding: 10px 16px 14px;
-  background: var(--surface);
-  border-top: 1px solid var(--border);
 }
 .vbtn {
   position: relative;

static_src/jbot/App.jsx

@@ -376,15 +376,17 @@ export default function App() {
           </section>
         </aside>
 
-        {/* ── Right column: memory + chat + hint + voice button ── */}
+        {/* ── Right column: memory + chat + bottom bar ── */}
         <div className="right-col">
           <MemoryPanel memories={memories} onMemoriesChange={refreshMemories} />
           <ChatPanel messages={chatMessages} voiceStatus={voiceStatus} />
-          <p className="right-hint">
-            按住 <kbd>Space</kbd> 或按钮说话 · 松开发送 · 🔊{' '}
-            <button className="hist-inline-link" onClick={() => navigate('/settings')}>{currentVoiceLabel}</button>
-          </p>
-          <VoiceButton phase={voicePhase} onStart={handleSpaceDown} onEnd={handleSpaceUp} />
+          <div className="right-footer">
+            <p className="right-hint">
+              按住 <kbd>Space</kbd> 或按钮说话 · 松开发送 · 🔊{' '}
+              <button className="hist-inline-link" onClick={() => navigate('/settings')}>{currentVoiceLabel}</button>
+            </p>
+            <VoiceButton phase={voicePhase} onStart={handleSpaceDown} onEnd={handleSpaceUp} />
+          </div>
         </div>
       </div>
     </div>