feat: add workflow CRUD commands and MCP workflow tools

[eskp]

Summary

• Adds kh wf create, kh wf delete, kh wf update CLI commands for programmatic workflow management
• Adds 8 static MCP tools to kh serve --mcp: workflow_list, workflow_get, workflow_create, workflow_update, workflow_delete, workflow_execute, execution_status, execution_logs
• Closes the gap between kh serve --mcp (action-only) and the keeperhub-mcp plugin (full workflow CRUD)

New Commands

Command	Description
kh wf create --name "X" [--nodes-file f.json]	Create workflow with optional node data from file or inline JSON
kh wf delete <id> [--yes]	Delete with confirmation prompt
kh wf update <id> [--name] [--nodes-file]	Update name, description, or nodes

MCP Static Tools

Registered via registerStaticTools() in cmd/serve/tools.go, separate from the dynamic schema-driven action tools:

Tool	Method	Endpoint
workflow_list	GET	/api/workflows
workflow_get	GET	/api/workflows/{id}
workflow_create	POST	/api/workflows/create
workflow_update	PATCH	/api/workflows/{id}
workflow_delete	DELETE	/api/workflows/{id}
workflow_execute	POST	/api/workflow/{id}/execute
execution_status	GET	/api/workflows/executions/{id}/status
execution_logs	GET	/api/workflows/executions/{id}/logs

Test plan

• kh wf create --name "Test" --host http://localhost:3000 --json returns workflow ID
• kh wf delete <id> --yes --host http://localhost:3000 deletes it
• kh wf update <id> --name "New" --host http://localhost:3000 updates it
• kh serve --mcp --host http://localhost:3000 exposes all 8 static tools alongside action tools
• go build ./... passes