Add fork/release docs, Apache-2.0 LICENSE, fork verification script and GitHub Action

[Bowenislandsong]

Motivation

• Establish clear upstream/fork guidance and release checklist so the project can be maintainable as a downstream of Code-OSS.
• Provide a permissive license (Apache-2.0) for project distribution and contributions.
• Add a lightweight verification to assert fork wiring / lineage and make that check runnable in CI.

Description

• Add LICENSE containing the Apache License 2.0 text for the repository.
• Replace and expand README.md with project overview, architecture, security baseline, license note, and next steps.
• Add docs/FORK_AND_RELEASE.md with step-by-step guidance for connected and detached fork models and a releasability checklist.
• Add scripts/verify-fork.sh, a bash script that checks for a configured upstream remote, validates it points to github.com/microsoft/vscode, and attempts to confirm ancestry to upstream/main when available.
• Add a GitHub Actions workflow ./github/workflows/fork-health.yml that runs the fork verification script on workflow_dispatch and on pushes affecting fork/release docs or the script itself.

Testing

• No automated CI runs were executed in this rollout; the repository now includes a Fork Health workflow that will run scripts/verify-fork.sh on manual dispatch or when relevant paths change.
• The scripts/verify-fork.sh logic was exercised locally to validate expected behavior when an upstream remote exists and when it does not.

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Codex Task