Replace outer session button with role=button div

Avoid nested buttons by converting the session list item container to a
focusable div with role=button and keyboard handlers (Enter/Space).
This preserves styling and a11y while eliminating invalid HTML nesting.

Validated via prettier, lint, and build.

Author: PeterDaveHello

src/pages/IndependentPanel/App.jsx

@@ -249,8 +249,9 @@ function App() {
               .filter((session) => Boolean(session.sessionId))
               .map((session) => (
                 <div role="listitem" key={session.sessionId}>
-                  <button
-                    type="button"
+                  <div
+                    role="button"
+                    tabIndex={0}
                     aria-pressed={sessionId === session.sessionId}
                     aria-current={sessionId === session.sessionId ? 'true' : undefined}
                     className={`normal-button chat-list-item ${
@@ -259,6 +260,12 @@ function App() {
                     onClick={() => {
                       setSessionIdSafe(session.sessionId)
                     }}
+                    onKeyDown={(e) => {
+                      if (e.key === 'Enter' || e.key === ' ') {
+                        e.preventDefault()
+                        setSessionIdSafe(session.sessionId)
+                      }
+                    }}
                   >
                     {session.sessionName}
                     <span
@@ -298,7 +305,7 @@ function App() {
                         }}
                       />
                     </span>
-                  </button>
+                  </div>
                 </div>
               ))}
           </div>