Fix tavily-mcp version metadata

[wowsofine]

Summary

• make tavily-mcp --version print the installed package version
• reuse the same package version for MCP server metadata
• add a packed-tarball metadata test that runs through npm exec

Reproduction

npm exec --yes --package=tavily-mcp@0.2.20 -- tavily-mcp --version currently prints unknown.

Root cause

The published bin runs through npm's .bin symlink path and yargs cannot infer the package version in that installed-package execution path. The new helper resolves the real entrypoint path, walks up to the installed package.json, and binds that version explicitly.

Validation

• Red test first: packed tarball test failed with unknown !== 0.2.20
• npm test
• local npm pack + npm exec --package=<tarball> -- tavily-mcp --version prints 0.2.20
• local npm pack + npm exec --package=<tarball> -- tavily-mcp --help
• git diff --check