chore: replace local changelog generator with @sapientpants/changelog-github-custom

[sapientpants]

Summary

• Replaced custom changelog implementation with the community package @sapientpants/changelog-github-custom
• Removed src/dev/changelog-custom.ts file
• Updated changeset configuration to use the external package

Changes

• Deleted custom changelog generator implementation
• Added @sapientpants/changelog-github-custom as a dev dependency
• Updated .changeset/config.json to reference the external package
• Updated .depcheckrc to ignore the new changelog package

Test plan

• All tests pass
• Linting passes
• Type checking passes
• Verify changeset version command works with new changelog generator
• Verify generated changelog format matches expectations

🤖 Generated with Claude Code

[Copilot]

Pull Request Overview

This PR replaces a custom changelog generator implementation with the community package @sapientpants/changelog-github-custom to simplify maintenance and leverage an established solution.

• Removed custom changelog implementation file and related dependencies
• Added @sapientpants/changelog-github-custom as a dev dependency
• Updated changeset configuration to use the external package

Reviewed Changes

Copilot reviewed 5 out of 6 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
src/dev/changelog-custom.ts	File deleted (custom changelog implementation removed)
package.json	Removed custom changelog dependencies, added external package
.depcheckrc	Added ignore rule for new changelog package
.changeset/use-changelog-github-custom.md	Added changeset documenting the migration
.changeset/config.json	Updated to reference external changelog package

Files not reviewed (1)

• pnpm-lock.yaml: Language not supported

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[deepsource-io]

Here's the code health analysis summary for commits db97f71..1ff4dc3. View details on DeepSource ↗.

Analysis Summary

Analyzer	Status	Summary	Link
Test coverage	✅ Success		View Check ↗
JavaScript	✅ Success	🎯 1 occurence resolved	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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