Add middleware-kit CLI for creating and updating projects

[johnnygreco]

What changed

• Added the middleware-kit package and its mkit command.
• Added mkit create for new Python and Rust middleware projects.
• Added mkit update to change a project to the latest OpenShell release or a release you choose.
• mkit update refreshes the proto, generated Python files or Rust build files, lockfile, and manifest. It leaves implementation files alone.
• Both commands build and check their changes in a temporary directory before touching the requested path.
• Updates work only on projects whose manifest names middleware-kit as the generator.

Tests

• uv run ruff format --check .
• uv run ruff check .
• uv run ty check
• uv run pytest — 85 tests, 95.50% coverage
• uv build
• Confirmed that the wheel installs the mkit command.
• In a clean test environment, installed mkit, created and tested Python and Rust projects, and updated a Python project. The update kept user files and caches intact and wrote the expected manifest and proto checksum.

Review

Correctness, security, maintainability, documentation, and UX reviewers checked the change. The UX reviewer ran the full create and update flows in an isolated environment. All reported issues were fixed, and the reviewers found no remaining problems.