feat: add claude md rules

[darkmavis1980]

Add CLAUDE.md linting rules

Summary of Changes 📋

• feat: Add CLAUDE.md ESLint plugin with max-lines rule to enforce line count limits
• feat: Add claude-md.config.js with dedicated ESLint configuration for linting CLAUDE.md files
• feat: Integrate CLAUDE.md linting into both index.js (Node) and browser.js (Browser/React) ESLint configurations
• feat: Add tests for CLAUDE.md linting rules and max-lines rule
• docs: Add ADR (docs/adr/0001-lint-claude-md-with-eslint.md) documenting the decision to lint CLAUDE.md with ESLint
• docs: Add examples/claude-md-usage.md with usage documentation for the new linting rules
• fix: Update test script to run Node.js tests instead of echo error
• chore: Add @eslint/markdown dependency
• chore: Update version to 4.3.0-next.1

Notes

This PR introduces a new ESLint plugin (plugins/claude-md/) that enforces a maximum line count on CLAUDE.md files, helping keep AI context files concise and maintainable. The plugin is automatically included in both the Node and Browser ESLint configurations exported by this package.

[davidding]

suggestion: Since the rule itself doesn't distinguish the file it is being run on - should we just use the built in https://eslint.org/docs/latest/rules/max-lines rule instead (and target CLAUDE.md with it)?

[darkmavis1980]

That's a good point, let me see if we can use that

[darkmavis1980]

According to Claude:

Good question — I looked into this. The built-in max-lines won't work here: CLAUDE.md is linted with language: 'markdown/gfm' (otherwise ESLint parses the Markdown as JS and errors), and the built-in rule listens on Program:exit while the Markdown AST's root node is root. So it would silently never fire, and it also calls JS-only SourceCode APIs (getAllComments, etc.) that the Markdown language doesn't provide. That's why this custom rule hooks root(). The "doesn't distinguish the file" point is true but harmless since files: ['**/CLAUDE.md'] already scopes it.

[craigayre]

Yeah I ummed and arred about leaving a similar comment - I think it does need to be a unique rule but there's potentially a mismatch between max-lines and it specifically mentioning CLAUDE.md. We could use this for SKILL.md with a different threshold etc so maybe the wording being generic would help?

You'd know what file from the output.