Additional build packaging improvements

[wmluke]

- What I did
Additional build packaging improvements

- How I did it

• Explicitly output module type extensions in dist (.mts, .mjs, .cts, or .cjs)
• Updated main in package.json to point to CJS for legacy node versions
• Added module to package.json to point to ESM for modern node version.

- How to verify it
Run tests in test-integration/cjs-project and test-integration/esm-project

- Human readable description for the release notes

[Copilot]

Pull Request Overview

This PR adds additional build packaging improvements to enhance module compatibility and build processes. The changes focus on enabling explicit module type extensions and improving the release workflow configuration.

• Added explicit module type extensions (.mts, .mjs, .cts, .cjs) to build output
• Updated package.json exports to properly handle both CommonJS and ESM modules
• Enhanced GitHub Actions release workflow with Git configuration

Reviewed Changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
tsdown.config.ts	Enables fixed extensions and node protocol for build output
package.json	Updates main/module fields and exports to use explicit file extensions
.github/workflows/release.yml	Adds Git configuration step for release workflow

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