[GuillaumeRx]

Explanation

Adds Changeset file validation to @metamask/changesets-lint.

The validator reports every problem it can recover from a single file, instead of stopping at the first error. It checks that each package is a workspace package and that each bump type is major, minor, or patch. It delegates summary grammar to @metamask/changesets-utils and converts summary-relative lines to file lines.

The parser recovers from malformed frontmatter so a broken YAML block still produces summary diagnostics. It matches the frontmatter delimiters accepted by the installed Changesets parser, and reports whether that parser accepts the file.

This PR contains no Git file selection, orchestration, or CLI. Those follow in later PRs.

References

• Follow-up PRs will add Git file selection and orchestration, then the CLI and documentation.

Checklist

• I've updated the test suite for new or updated code as appropriate
• I've updated documentation (JSDoc, Markdown, etc.) for new or updated code as appropriate
• I've communicated my changes to consumers by updating changelogs for packages I've changed
• I've introduced breaking changes in this PR and have prepared draft pull requests for clients and consumer packages to resolve them

[mcmire]

Left some suggestions and a question below.

[mcmire]

LGTM!