fix(desktop): route Bot Mode group-chat Markdown through the plugin SDK

Follow-up to the cherry-picked fix for #88391: the bare `streamdown` import
broke the plugin's side-load contract (vm-harness tests and the legacy-sdk
tmpdir loader can't resolve bare specifiers, and the runtime plugin door only
maps @hermes/plugin-sdk and react). Export Streamdown from the SDK instead,
feature-detect it in plugin.js like SkillsView/McpTab (plain-text fallback on
older desktops), and fix the indentation at the render site.

apps/desktop/src/plugins/hermes-bots/plugin.js

@@ -16,7 +16,6 @@
  */
 
 import * as sdk from '@hermes/plugin-sdk'
-import { Streamdown } from 'streamdown'
 import {
   atom,
   Button,
@@ -68,6 +67,7 @@ import { jsx, jsxs } from 'react/jsx-runtime'
 const { McpTab, ToolsetConfigPanel } = sdk
 // Keep optional exports feature-detected; test harnesses may strip the SDK namespace.
 const SkillsView = typeof sdk === 'undefined' ? undefined : sdk.SkillsView
+const Streamdown = typeof sdk === 'undefined' ? undefined : sdk.Streamdown
 
 const ID = 'hermes-bots'
 const ROSTER_KEY = [ID, 'roster']
@@ -6492,8 +6492,8 @@ function GroupChatWorkspace({ group, members }) {
                         ]
                       }),
                       jsx('div', {
-    className: 'text-xs text-(--ui-text-secondary) [&_p]:mb-1 [&_p:last-child]:mb-0',
-    children: jsx(Streamdown, { children: entry.text })
+                        className: 'text-xs text-(--ui-text-secondary) [&_p]:mb-1 [&_p:last-child]:mb-0',
+                        children: Streamdown ? jsx(Streamdown, { children: entry.text }) : entry.text
                       })
                     ]
                   }, `${entry.at}:${index}`)

apps/desktop/src/sdk/index.ts

@@ -633,3 +633,6 @@ export { useMutation, useQuery, useQueryClient } from '@tanstack/react-query'
 /** Plugin-local reactive state (share between a trigger and its panel, poll
  *  loops, cross-component signals) — the same primitive `host.state` uses. */
 export { atom, computed } from 'nanostores'
+/** Markdown renderer (same pipeline core chat surfaces use) so plugins render
+ *  message text as a preview instead of raw Markdown source. */
+export { Streamdown } from 'streamdown'