chore: remove redundant build step from main workflow

[sapientpants]

Summary

Removes an unnecessary build step from the main workflow that was running before version management.

Changes

• ✅ Removed redundant "Build for changeset" step from main.yml
• ✅ Cleaned up orphaned dist/dev directory containing stale build artifacts
• ✅ Workflow validation passes (actionlint)

Rationale

The removed build step was unnecessary because:

• The changeset system uses the npm package changelog-github-custom, not local TypeScript code
• The misleading comment claimed a custom changelog needed to be built, but it's actually an npm dependency
• The second build step (after version detection) handles all actual build requirements

Impact

• 🚀 Reduces CI pipeline execution time by ~30 seconds on each main branch push
• 📦 Simplifies the workflow by removing redundant operations
• 🧹 Cleans up stale build artifacts that weren't being used

Testing

• ✅ Workflow syntax validated with actionlint
• ✅ Changeset version command tested locally (works without the build)
• ✅ All pre-commit hooks pass

[Copilot]

Pull Request Overview

This PR removes an unnecessary build step from the GitHub Actions main workflow that was running before version management. The removed build was originally intended to compile a custom changelog generator, but the actual implementation uses an npm package instead.

• Removes redundant "Build for changeset" step from the CI pipeline
• Eliminates misleading comments about custom TypeScript changelog generation
• Streamlines workflow execution by removing unnecessary operations

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[deepsource-io]

Here's the code health analysis summary for commits 797e864..921989c. View details on DeepSource ↗.

Analysis Summary

Analyzer	Status	Summary	Link
Test coverage	✅ Success		View Check ↗
JavaScript	✅ Success		View Check ↗

Code Coverage Report

Metric	Aggregate	Javascript
Branch Coverage	88%	88%
Composite Coverage	89.6%	89.6%
Line Coverage	90%	90%

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