fix: update bundled DeepSeek Harness to rc.8

The desktop runtime still pinned the rc.6 Harness family. It now uses the coherent rc.8 package set, adapts the revised image-attachment limits and error contract, and derives release checks from the lockfile. The managed SSH Agent package remains unchanged.

Release note: 内置 DeepSeek Harness 已升级至 0.1.0-rc.8，并适配新版图片附件限制；托管 SSH Agent 包不受影响。

src/renderer/src/SettingsPanel.test.tsx

@@ -171,7 +171,7 @@ const detectAgentRuntimes = vi.fn<
   deepseekHarness: {
     available: true,
     path: 'bundled://deepseek-harness',
-    version: '0.1.0-rc.6',
+    version: '0.1.0-rc.8',
     source: 'bundled',
     detail: '内置 Harness Adapter 已就绪'
   }
@@ -2665,11 +2665,11 @@ describe('SettingsPanel runtime files', () => {
       )
     ).toHaveClass('runtime-overview__path')
     expect(
-      within(harnessOverview).getByText('0.1.0-rc.6')
+      within(harnessOverview).getByText('0.1.0-rc.8')
     ).toBeInTheDocument()
     expect(
       within(harnessOverview).getByText(
-        '内置 DeepSeek Harness 0.1.0-rc.6 已就绪'
+        '内置 DeepSeek Harness 0.1.0-rc.8 已就绪'
       )
     ).toBeInTheDocument()
     expect(