docs: add comprehensive MCP documentation and examples

- docs/mcp.md: Full MCP documentation covering prerequisites, configuration,
  transports (stdio + HTTP), security (env filtering, credential stripping),
  reconnection, troubleshooting, popular servers, and advanced usage
- README.md: Add MCP section with quick config example and install instructions
- cli-config.yaml.example: Add commented mcp_servers section with examples
  for stdio, HTTP, and authenticated server configs
- docs/tools.md: Add MCP to Tool Categories table and MCP Tools section
- skills/mcp/native-mcp/SKILL.md: Create native MCP client skill with
  full configuration reference, transport types, security, troubleshooting
- skills/mcp/DESCRIPTION.md: Update category description to cover both
  native MCP client and mcporter bridge approaches

cli-config.yaml.example

@@ -442,6 +442,41 @@ toolsets:
 # toolsets:
 #   - safe
 
+# =============================================================================
+# MCP (Model Context Protocol) Servers
+# =============================================================================
+# Connect to external MCP servers to add tools from the MCP ecosystem.
+# Each server's tools are automatically discovered and registered.
+# See docs/mcp.md for full documentation.
+#
+# Stdio servers (spawn a subprocess):
+#   command: the executable to run
+#   args: command-line arguments
+#   env: environment variables (only these + safe defaults passed to subprocess)
+#
+# HTTP servers (connect to a URL):
+#   url: the MCP server endpoint
+#   headers: HTTP headers (e.g., for authentication)
+#
+# Optional per-server settings:
+#   timeout: tool call timeout in seconds (default: 120)
+#   connect_timeout: initial connection timeout (default: 60)
+#
+# mcp_servers:
+#   time:
+#     command: uvx
+#     args: ["mcp-server-time"]
+#   filesystem:
+#     command: npx
+#     args: ["-y", "@modelcontextprotocol/server-filesystem", "/home/user"]
+#   notion:
+#     url: https://mcp.notion.com/mcp
+#   github:
+#     command: npx
+#     args: ["-y", "@modelcontextprotocol/server-github"]
+#     env:
+#       GITHUB_PERSONAL_ACCESS_TOKEN: "ghp_..."
+
 # =============================================================================
 # Voice Transcription (Speech-to-Text)
 # =============================================================================