feat: add --version flag to CLI

[dastratakos]

Summary

Add stagereview --version support so users can check which version they have installed.

Changes

• Use Commander's built-in .version() to register the --version / -V flag
• Read the version from package.json at runtime via createRequire

Testing

• pnpm typecheck, pnpm lint, and pnpm test all pass
• Built and verified stagereview --version outputs 0.1.2

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[gemini-code-assist]

Code Review

This pull request introduces dynamic versioning for the CLI by reading the version directly from package.json. The reviewer suggests extending this approach to include the package name as well, which would further improve maintainability by centralizing configuration.