docs: add AIRIS MCP Gateway as unified installation option (#499)

* docs: add AIRIS MCP Gateway as unified installation option

Adds airis-mcp-gateway as an alternative MCP setup method that provides:
- Single SSE endpoint for all MCP servers
- HOT/COLD server management for token optimization
- Lazy loading (servers start on-demand)
- Unified tool discovery
- Web UI for management

This addresses the complexity of managing multiple MCP servers and
provides token-efficient operation through selective tool advertising.

Repository: github.com/agiletec-inc/airis-mcp-gateway

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

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

* fix(docs): update AIRIS MCP Gateway installation instructions

- Replace outdated docker-compose.dist.yml method with quick-install.sh
- Fix Claude Code registration command: use --transport sse instead of npx mcp-remote
- Update feature list: 27+ tools, 75-90% token reduction, 120s idle timeout
- Add verification commands (health check, tools count)
- Update HOT/COLD server examples with actual server names
- Add AIRIS Suite reference (airis-agent, mindbase, airis-workspace)

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

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

* fix(mcp): update airis configs to recommend airis-mcp-gateway

- Update mcp-servers.md: remove quick-install.sh, use git clone + docker compose
- Update MCP_Airis-Agent.md: recommend gateway, list current tools
- Update MCP_Mindbase.md: recommend gateway, list current tools
- Add deprecation notice to airis-agent.json and mindbase.json configs
- Change airis-agent config from Docker to uvx

All airis components (airis-agent, mindbase) are now included in airis-mcp-gateway.
Individual installation is deprecated in favor of the unified gateway.

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

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

---------

Co-authored-by: kazuki <kazuki@kazukinoMacBook-Air.local>
Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>

docs/user-guide/mcp-servers.md

@@ -167,6 +167,46 @@ export TAVILY_API_KEY="tvly-your_api_key_here"
 - `--depth deep`: 20-40 sources, comprehensive analysis
 - `--depth exhaustive`: 40+ sources, academic-level research
 
+## Unified MCP Gateway (Alternative Setup)
+
+For users who want a simpler, unified setup that manages all MCP servers through a single endpoint, **AIRIS MCP Gateway** provides:
+
+- **50 tools** from 7 default servers (airis-agent, context7, fetch, memory, sequential-thinking, serena, tavily)
+- **Single SSE endpoint** instead of 8+ separate stdio connections
+- **Lazy loading** - servers start only when needed, auto-terminate when idle
+
+### Setup
+
+```bash
+# 1. Clone and start
+git clone https://github.com/agiletec-inc/airis-mcp-gateway.git
+cd airis-mcp-gateway
+docker compose up -d
+
+# 2. Register with Claude Code
+claude mcp add --scope user --transport sse airis-mcp-gateway http://localhost:9400/sse
+```
+
+### Verify
+
+```bash
+curl http://localhost:9400/health
+curl http://localhost:9400/api/tools/combined | jq '.tools_count'
+```
+
+### Configuration
+
+Edit `mcp-config.json` to enable/disable servers, then restart:
+```bash
+docker compose restart api
+```
+
+### More Information
+
+- **Repository**: [github.com/agiletec-inc/airis-mcp-gateway](https://github.com/agiletec-inc/airis-mcp-gateway)
+
+---
+
 ## Configuration
 
 **MCP Configuration File (`~/.claude.json`):**