feat(quality): add markdownlint-cli2 to quality checks (#1039)

- Add markdownlint-cli2 as dev dependency
- Add lint:md script to package.json
- Add markdownlint job to CI workflow
- Configure 5 rules: heading-increment, no-duplicate-heading,
  no-trailing-punctuation, no-bare-urls, no-space-in-emphasis
- Fix existing violations across 19 markdown files
- No auto-fix to prevent destructive changes

Closes #1034

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-authored-by: Claude <noreply@anthropic.com>
Co-authored-by: Brian <bmadcode@gmail.com>

src/modules/bmm/docs/faq.md

@@ -532,7 +532,7 @@ Trust your expertise - BMM supports your decisions.
 
 ### Q: How do I report a bug or request a feature?
 
-**A:** Open a GitHub issue at: https://github.com/bmad-code-org/BMAD-METHOD/issues
+**A:** Open a GitHub issue at: <https://github.com/bmad-code-org/BMAD-METHOD/issues>
 
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