fix: remove internal orchestration docs from public site

Remove Orchestration Showcase Plan and Orchestration Acceptance Harness
pages — these are internal planning documents, not public documentation.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: 1broseidon

docs/.vitepress/config.ts

@@ -325,8 +325,6 @@ export default withMermaid(defineConfig({
           { text: 'Agent Workflows', link: '/guides/agent-workflows' },
           { text: 'Orchestration', link: '/guides/orchestration' },
           { text: 'Orchestration Workflows', link: '/guides/orchestration-workflows' },
-          { text: 'Orchestration Showcase Plan', link: '/guides/orchestration-showcase-plan' },
-          { text: 'Orchestration Acceptance Harness', link: '/guides/orchestration-acceptance' },
         ],
       },
       {