Add MCP server exposing workflow engine to AI assistants

[Copilot]

Introduces a Model Context Protocol (MCP) server that dynamically exposes workflow engine functionality—module types, step types, config validation, schema generation, plugin listing—so AI tools can author and validate workflow YAML with accurate, up-to-date knowledge.

New packages

• mcp/ — Server implementation using github.com/mark3labs/mcp-go v0.27.0 over stdio transport
• cmd/mcp/ — Entry point binary (workflow-mcp-server)

Tools (8)

• list_module_types / list_step_types / list_trigger_types / list_workflow_types — enumerate available types from schema registry (reflects plugins dynamically)
• validate_config — validates YAML string using same logic as wfctl validate
• inspect_config — returns structured summary with dependency graph
• generate_schema — produces JSON Schema for config files
• get_config_skeleton — generates template YAML for given module types
• list_plugins — scans plugin directory for installed external plugins

Resources (3)

• workflow://docs/overview — architecture and key concepts
• workflow://docs/yaml-syntax — config file syntax guide
• workflow://docs/module-reference — dynamically generated from schema.KnownModuleTypes()

Installation

{
  "mcpServers": {
    "workflow": {
      "command": "/path/to/workflow-mcp-server",
      "args": ["-plugin-dir", "/path/to/data/plugins"]
    }
  }
}

Works with Claude Desktop, VS Code/Copilot, Cursor, or any MCP-compatible client. Full docs in docs/mcp.md.

Other changes

• Makefile: added build-mcp target
• 21 unit tests with race detection coverage across all tools and resources

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[Copilot]

Pull request overview

This PR introduces Model Context Protocol (MCP) server functionality to expose the workflow engine to AI assistants. The MCP server enables AI tools to dynamically discover module types, validate configurations, generate schemas, and access documentation—all reflecting the current state of the engine including any loaded plugins.

Changes:

• Added MCP server package (mcp/) implementing 8 tools and 3 documentation resources
• Created entry point binary (cmd/mcp/) for stdio-based MCP communication
• Added comprehensive test coverage (21 unit tests) with race detection
• Updated build system with build-mcp Makefile target

Reviewed changes

Copilot reviewed 7 out of 8 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
mcp/server.go	Core MCP server implementation with tool/resource handlers
mcp/server_test.go	Comprehensive unit tests for all tools and resources
mcp/docs.go	Embedded documentation strings for MCP resources
cmd/mcp/main.go	Entry point binary for stdio MCP server
go.mod / go.sum	Added mcp-go v0.27.0 dependency and transitive deps
docs/mcp.md	User-facing documentation for MCP server setup and usage
Makefile	Added build-mcp target

Comments suppressed due to low confidence (3)

mcp/server_test.go:83

• This will panic if any step type is shorter than 5 characters. Use strings.HasPrefix(str, \"step.\") instead to safely check the prefix.

		if str[:5] != "step." {

mcp/server_test.go:364

• This JSON unmarshal operation appears to serve no purpose—it unmarshals an empty object into a throw-away variable. Consider removing these lines.

	if err := json.Unmarshal([]byte("{}"), new(any)); err != nil {
		t.Fatal(err)
	}

mcp/server.go:542

• The comment correctly notes that strings.Title is deprecated (SA1019). Consider using cases.Title(language.English).String(prefix) from golang.org/x/text/cases for a non-deprecated alternative.

		fmt.Fprintf(&b, "## %s\n\n", strings.Title(prefix)) //nolint:staticcheck // SA1019: strings.Title is fine for docs