feat(journal): delete sessions from the ui

Add a confirmation dialog that spells out the removal is irreversible, and expose delete from the GM session dropdown and the lobby session list.

src/components/journal/SessionDropdown.tsx

@@ -10,6 +10,7 @@ import {
 
 interface SessionDropdownProps {
   onCreate: () => void;
+  onDelete: (id: string, name: string) => void;
 }
 
 export const SessionDropdown: Component<SessionDropdownProps> = (props) => {
@@ -54,22 +55,37 @@ export const SessionDropdown: Component<SessionDropdownProps> = (props) => {
         >
           <For each={Object.entries(manifest().sessions)}>
             {([id, meta]) => (
-              <button
-                onClick={(e) => {
-                  e.stopPropagation();
-                  handleSessionSelect(id);
-                }}
-                class={`w-full text-left px-3 py-1 text-xs hover:bg-gray-100 flex items-center gap-1 ${
-                  id === stream.sessionId
-                    ? "bg-blue-50 text-blue-700"
-                    : "text-gray-700"
+              <div
+                class={`flex items-center ${
+                  id === stream.sessionId ? "bg-blue-50" : ""
                 }`}
               >
-                <span class="truncate flex-1">{meta.name || id}</span>
-                <Show when={id === stream.sessionId}>
-                  <span class="text-blue-500 shrink-0">✓</span>
-                </Show>
-              </button>
+                <button
+                  onClick={(e) => {
+                    e.stopPropagation();
+                    handleSessionSelect(id);
+                  }}
+                  class={`flex-1 min-w-0 text-left px-3 py-1 text-xs hover:bg-gray-100 flex items-center gap-1 ${
+                    id === stream.sessionId ? "text-blue-700" : "text-gray-700"
+                  }`}
+                >
+                  <span class="truncate flex-1">{meta.name || id}</span>
+                  <Show when={id === stream.sessionId}>
+                    <span class="text-blue-500 shrink-0">✓</span>
+                  </Show>
+                </button>
+                <button
+                  onClick={(e) => {
+                    e.stopPropagation();
+                    setDropdownOpen(false);
+                    props.onDelete(id, meta.name || id);
+                  }}
+                  class="shrink-0 px-2 py-1 text-[10px] text-gray-300 hover:text-red-500"
+                  title="删除会话"
+                >
+                  🗑
+                </button>
+              </div>
             )}
           </For>
           <div class="border-t border-gray-100 my-0.5" />