[Discovery] mcp/sequentialthinking - Chain of Thought Reasoning

## Project Association

This issue tracks the `sequentialthinking` MCP server in the core profile.

### Server Details
- **Name**: sequentialthinking (thinking)
- **Source**: https://github.com/modelcontextprotocol/servers/tree/main/src/sequentialthinking
- **Docker Hub**: https://hub.docker.com/r/mcp/sequentialthinking
- **Category**: reasoning
- **Language**: TypeScript/Node.js

### Transport Status
- **Current**: stdio only (upstream)
- **Implementation**: HTTP-wrapped via supergateway
- **Docker Image**: `sequential-thinking-mcp:http` (custom build)

### Tools Provided
- `sequentialthinking`: Dynamic problem-solving through thought chains
- Supports thought revision and branching
- Flexible chain length adjustment
- Hypothesis generation and verification

### Docker Status
- Official image: `mcp/sequentialthinking`
- Custom wrapper: `sequential-thinking.dockerfile`
- HADOLint: Not checked

### Notes
- Official Anthropic server
- Core reasoning capability for complex problem-solving
- Consider alternatives: code-reasoning, MAS-sequential-thinking

### Tracking
- [ ] Document thought chain parameters
- [ ] HADOLint compliance check
- [ ] Compare with alternative reasoning servers
- [ ] Consider Rust rewrite