[Registry]: Define metadata for `cmd_args` that a user can provide when running an MCP server

TL;DR: The registry should provide metadata about command arguments, so that users know what options are available, and which are required.

Ultimately, the goal of this issue is to allow a better UX for the user interface, so that we may be able to render dedicated fields per-argument.

Take for example the PostgreSQL MCP server

Today, the only way a user can learn how to supply a DB url is by looking into the documentation for the server.

The documentation suggests that it should be configured like this:

{
  "mcpServers": {
    "postgres": {
      "command": "npx",
      "args": [
        "-y",
        "@modelcontextprotocol/server-postgres",
        "postgresql://localhost/mydb"
      ]
    }
  }
}

With the DB url supplied as a positional argument.

See the result of thv registry info postgres:

Name: postgres
Image: mcp/postgres:latest
Description: A Model Context Protocol server that provides read-only access to PostgreSQL databases. This server enables LLMs to inspect database schemas and execute read-only queries.
Transport: stdio
Repository URL: https://github.com/modelcontextprotocol/servers
Popularity: 49668 stars, 9095 pulls
Last Updated: 2025-05-29T00:21:13Z
Tools:
  - query
Tags:
  database, postgres, postgresql, query, read-only, schema, sql
Permissions:
  Read:
    - /tmp/db
  Write:
    - /tmp/db
  Network:
    Allow Transport: tcp
    Allow Port: 443
Example Command:
  thv run postgres

No info is provided on the positional DB URL argument.

Start by tracing the registry representation behind thv registry info and the cmd_args metadata named in the issue. Determine how positional and required arguments should be represented, then verify that the PostgreSQL example exposes the database URL and whether it is required.