Ci/fork safe test build

[MLittleprince]

Summary

• add a read-only MemOS CLI — Safe Test & Build workflow for pushes, pull requests, and manual runs
• run Python unit tests and installed CLI smoke tests
• build and smoke-test the existing Linux and Windows CLI packages
• upload temporary Linux and Windows test artifacts with 7-day retention
• fix packaged Windows CLI help output failing on legacy cp1252 streams

Fork behavior

Contributors can run the workflow in their own repository after pushing code or opening a pull request.

The workflow only performs tests and temporary builds. It cannot create tags, GitHub Releases, npm packages, Doc Agent requests, Docs PRs, or deployments.

A fork PR merged into the official main branch is still handled by the official repository’s existing release workflow.

Validation

• Python unit tests passed
• CLI --version and --help passed
• Linux package build and smoke test passed
• Windows package build and smoke test passed
• Linux and Windows temporary artifacts were uploaded
• existing CLI release-contract tests passed
• workflow permissions and sensitive-content scan passed

Remote validation: https://github.com/MemTensor/MemOS-Cloud-CLI/actions/runs/32801371211

Safety

• permissions: contents: read
• checkout credentials are not persisted
• no repository or release secrets are used
• no pull_request_target
• no tag, Release, npm publish, Doc Agent, docs sync, or deployment operations