chore: migrate from deprecated @anthropic-ai/claude-code to @anthropic-ai/claude-agent-sdk

Anthropic rebranded the SDK in 2025 from "Claude Code SDK" to "Claude Agent SDK". Updated all references across package.json, Dockerfile, and documentation to use the current @anthropic-ai/claude-agent-sdk package.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

package.json

@@ -7,7 +7,6 @@
     "start": "./shannon.mjs"
   },
   "dependencies": {
-    "@anthropic-ai/claude-code": "^1.0.96",
     "@anthropic-ai/claude-agent-sdk": "^0.1.0",
     "ajv": "^8.12.0",
     "ajv-formats": "^2.1.1",