fix(chat): wire Sanity Context Knowledge Base MCP tools and org token fallback for Agent AJ

[codercatdev]

Summary

• Expose all tools returned by the Sanity Context MCP endpoint (https://api.sanity.io/v1/context/organizations/ovF2qiKSO/mcp/agent-aj-mcp), including initial_context and knowledge_base_read for the AJ Knowlege Jokes Knowledge Base, in /api/chat.
• Pre-fetch initial_context outline when available and include it in Agent AJ's system prompt so knowledgeBaseId and entry paths are immediately available on Step 1.
• Add MCP tool output fallback synthesis when models complete tool calls without emitting trailing text deltas.
• Add token resolution fallback (SANITY_CONTEXT_TOKEN, SANITY_AUTH_TOKEN, SANITY_API_READ_TOKEN, SANITY_API_WRITE_TOKEN) and sync SANITY_AUTH_TOKEN / SANITY_CONTEXT_TOKEN to Cloudflare Workers in deploy-workers.yml.
• Expose knowledge_base_read in /api/mcp and /.well-known/mcp/server-card.json, and add a Coding joke quick prompt chip in ChatModal.astro.

[github-actions]

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