feat: add Sequential Thinking MCP server definition

Add Sequential Thinking local stdio server via npx
@modelcontextprotocol/server-sequential-thinking.
Structured step-by-step reasoning with branching and revision.

https://claude.ai/code/session_013AxurW8hPAfnUNvik354Xx

Author: claude

servers/community.sequential-thinking.json

@@ -0,0 +1,45 @@
+{
+  "$schema": "../schemas/server-definition.schema.json",
+  "id": "community.sequential-thinking",
+  "name": "Sequential Thinking",
+  "alias": "think",
+  "description": "Dynamic step-by-step problem solving with branching, revision, and hypothesis validation. Helps LLMs break down complex problems through structured reasoning.",
+  "icon": "https://avatars.githubusercontent.com/u/182288589?v=4",
+  "schema_version": "2.1",
+  "categories": ["ai-ml", "developer-tools"],
+  "tags": ["thinking", "reasoning", "problem-solving", "chain-of-thought", "planning", "analysis"],
+
+  "transport": {
+    "type": "stdio",
+    "command": "npx",
+    "args": ["-y", "@modelcontextprotocol/server-sequential-thinking"],
+    "metadata": {
+      "inputs": []
+    }
+  },
+
+  "auth": {
+    "type": "none"
+  },
+
+  "contributor": {
+    "name": "Model Context Protocol",
+    "github": "modelcontextprotocol",
+    "url": "https://modelcontextprotocol.io"
+  },
+
+  "links": {
+    "repository": "https://github.com/modelcontextprotocol/servers",
+    "homepage": "https://modelcontextprotocol.io",
+    "documentation": "https://github.com/modelcontextprotocol/servers/blob/main/src/sequentialthinking/README.md"
+  },
+
+  "platforms": ["all"],
+
+  "capabilities": {
+    "tools": true,
+    "resources": false,
+    "prompts": false,
+    "read_only_mode": true
+  }
+}