Add blog: Unified agent experience

Add a new blog post announcing the unified agent experience in VS Code, including OpenAI Codex integration, Agent Sessions, the new Plan agent, and subagents (#runSubagent). Add the post markdown (blogs/2025/11/03/unified-agent-experience.md) and the social header image (blogs/2025/11/03/unified-agent-experience.png).

Author: burkeholland

blogs/2025/11/03/universe-recap.md renamed to blogs/2025/11/03/unified-agent-experience.md

@@ -3,7 +3,7 @@ Order: 108
 TOCTitle: A Unfied Agent Experience
 PageTitle: A Unified Experience for all Coding Agents
 Agents took over VS Code in 2025. We released [agent mode](https://code.visualstudio.com/blogs/2025/02/24/introducing-copilot-agent-mode) for VS Code, integration for the [Copilot coding agent (cloud)](https://code.visualstudio.com/docs/copilot/copilot-coding-agent), and the new [GitHub Copilot CLI](https://github.com/features/copilot/cli/). But Copilot is not the only agent game in town. There are now more coding agents than ever - including options from OpenAI and Anthropic.
-MetaSocialImage: expanding-model-choice.png
+MetaSocialImage: unified-agent-experience.png
 Date: 2025-11-04
 Author: Burke Holland
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