Add create command to publisher CLI for generating server.json files

[Copilot]

This PR adds a new create command to the MCP Registry Publisher CLI tool that generates properly formatted server.json files from command-line flags, addressing the difficulty of manually creating these files.

Changes Made

Core Implementation

• Restructured CLI: Modified main.go to support subcommands (publish and create)
• Backward Compatibility: Existing publish command functionality remains unchanged
• Human-Friendly Flags: Added intuitive flag names with both long and short versions

Create Command Features

Required Flags

• --name, -n: Server name (e.g., io.github.owner/repo-name)
• --description, -d: Server description
• --repo-url: Repository URL

Optional Flags

• --execute, -e: Command invocation that generates runtime arguments
• --version, -v: Server version (default: "1.0.0")
• --env-var: Environment variables in format NAME:DESCRIPTION (repeatable)
• --package-arg: Package arguments in format VALUE:DESCRIPTION (repeatable)
• --runtime-hint: Runtime hint (e.g., "docker")
• --registry: Package registry name (default: "npm")
• --output, -o: Output file path (default: "server.json")

Smart Command Parsing

The --execute flag intelligently parses command invocations:

# Example: Docker command with complex arguments
./bin/mcp-publisher create \
  --name "io.github.example/docker-server" \
  --description "Docker-based MCP server" \
  --repo-url "https://github.com/example/docker-server" \
  --execute "docker run --rm -v /data:/app/data example/server --config=/path/config.json"

Generates runtime arguments with context-aware descriptions:

• Detects command flags (--rm, --config)
• Identifies flag values (/path/config.json for --config)
• Handles complex Docker mount syntax
• Supports quoted strings and special characters

Generated Output

Creates complete server.json files with:

• Server metadata (name, description, version, repository)
• Package configuration with registry details
• Runtime arguments parsed from execute command
• Environment variables with descriptions
• Package arguments for user configuration

Documentation

• Updated README with comprehensive usage examples
• Added examples for NPX, Docker, and complex server configurations
• Documented all available flags and their purposes
• Maintained existing publish command documentation

Example Usage

# Basic NPX server
./bin/mcp-publisher create \
  --name "io.github.example/my-server" \
  --description "My MCP server" \
  --repo-url "https://github.com/example/my-server" \
  --execute "npx @example/my-server --verbose" \
  --env-var "API_KEY:Your API key"

# Docker server with complex configuration
./bin/mcp-publisher create \
  --name "io.github.example/docker-server" \
  --description "Docker-based server" \
  --repo-url "https://github.com/example/docker-server" \
  --runtime-hint "docker" \
  --execute "docker run --mount type=bind,src=/data,dst=/app/data example/server" \
  --package-arg "--workspace:Specify workspace directory"

The generated files provide a solid foundation that users can then edit to fine-tune descriptions, set argument requirements, and add remote server configurations.

Fixes #151.

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