chore: Add `_experiment` directories to markdownlint, Prettier, and ESLint ignore lists.

.markdownlint-cli2.yaml

@@ -7,6 +7,7 @@ ignores:
   - CODE_OF_CONDUCT.md
   - _bmad/**
   - _bmad*/**
+  - _experiment/**
   - .agent/**
   - .claude/**
   - .roo/**

.prettierignore

@@ -8,5 +8,8 @@ CODE_OF_CONDUCT.md
 _bmad/
 _bmad*/
 
+# Experiment folders
+_experiment/
+
 # IDE integration folders (user-specific, not in repo)
 .junie/

eslint.config.mjs

@@ -14,6 +14,7 @@ export default [
       'test/template-test-generator/**',
       'test/fixtures/**',
       '_bmad*/**',
+      '_experiment/**',
       // Build output
       'build/**',
       // Website uses ESM/Astro - separate linting ecosystem