[luojiyin1987]

Summary

• Upgrade @lint-md/core to ^2.6.0. Keep package-lock.json ignored.
• Route .mdx lint to lintMdx(). Load the MDX entry only for MDX files.
• Match .MDX during file discovery. Test both extensions through the CLI.
• Reject MDX --fix requests before file changes. Preserve the behavior from fix(cli): prevent unsafe --fix on MDX files #208.
• Test JSX attributes, ESM, expressions, Markdown lint, and MDX fix rejection.
• Check MDX lint from the installed package.

Checks

• npm run lint
• npm test -- --runInBand --silent (255 tests passed)
• npm run test:package

Memory check

• Ran five Markdown trials for one worker and four workers on the same host.
• Median peak RSS rose from 111,380 to 122,048 KiB with one worker.
• Median peak RSS rose from 267,124 to 289,720 KiB with four workers.
• These runs show no RSS reduction. The Markdown worker does not load either MDX module.

No sensitive data appears in this PR. No redactions were needed.