[Feature]: Add OpenHarmony OHPM registry adapter

## Summary

Add first-class OpenCLI support for the OpenHarmony OHPM package registry at https://ohpm.openharmony.cn/.

## Motivation

OHPM is the package registry used by OpenHarmony/HarmonyOS third-party libraries. Today agents need to inspect the SPA manually to search packages, view package metadata, or list hot keywords/dependents. A built-in adapter would make this data available through stable CLI commands.

## Proposed commands

- `ohpm search `: search registry packages using the public OHPM search endpoint.
- `ohpm package `: fetch package metadata such as version, downloads, license, repository, dependencies, dependents, and publish date.
- `ohpm dependents `: list packages that depend on a package.
- `ohpm keywords`: list hot search keywords from the OHPM home page.

## Notes

The public SPA endpoints are available under `/ohpmweb/registry/oh-package/openapi`. The search API accepts `sortedType` values `relevancy`, `likes`, and `latest`; values like `download` and `popular` are rejected by the server.

Start by reviewing existing OpenCLI registry adapters and the OHPM endpoints under /ohpmweb/registry/openapi. Verify the accepted sortedType values against the public search API, then implement the search, package, dependents, and keywords commands. Done means each command exposes the corresponding OHPM data through stable CLI output.

Written by the indexing model from the issue text.