feat(desktop): add zhihu publish adapter

Ship a Zhihu publish adapter that reuses the shared session fetch and
image pipeline: converts markdown to HTML via marked, uploads cover
and inline images through Zhihu's image token flow, creates a draft,
and publishes it, returning external article URLs. Wire it into the
adapter barrel and runtime-controller's publish adapter selector so
Zhihu publish tasks stop falling through to the scaffold result.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

apps/desktop-client/src/main/runtime-controller.ts

@@ -13,6 +13,7 @@ import type {
 import {
   doubaoAdapter,
   toutiaoAdapter,
+  zhihuAdapter,
   type AdapterExecutionResult,
   type MonitorAdapter,
   type PublishAdapter,
@@ -1150,6 +1151,9 @@ function selectPublishAdapter(platform: string): PublishAdapter | null {
   if (platform === toutiaoAdapter.platform) {
     return toutiaoAdapter;
   }
+  if (platform === zhihuAdapter.platform) {
+    return zhihuAdapter;
+  }
   return null;
 }