refactor(web): move the produced-files row into its own plugin package

ui-conversation now owns only the conversation.chat.turnTail hole; the row,
its derivation, and its copy live in @deepseek-ai/dsh-client-ui-deliverables,
composed in or out by one cordis.yml line.

packages/client/ui-deliverables/src/index.ts

@@ -0,0 +1,9 @@
+/**
+ * Deliverables plugin, node half. Pure UI plugin: the empty apply exists so
+ * the plugin appears in the host cordis.yml / Loader; the browser half ships
+ * via exports["./client"], discovered through the package.json dshClient
+ * declaration.
+ */
+
+/** Host plugin body — no host-side behavior for this surface plugin. */
+export function apply(): void {}