fix: correct AI workflow doc file references to prevent read:file_not_found errors

- folder-structure.md: fix includes/core.php → Core.php, plugin.php → Plugin.php,
  updater.php → Updater.php (PascalCase matches actual filenames on disk)
- bug-fixing.md: fix fix-plugin-does-not-exist-notices.php →
  wp-fix-plugin-does-not-exist-notices.php (correct wp- prefix) and
  languages/fix-plugin... → languages/wp-fix-plugin... (same prefix fix)
- feature-development.md: remove reference to non-existent reference-plugins/
  directory to stop read:file_not_found errors when AI follows the docs

Addresses contributor insight issue #16: incorrect file paths in AI workflow
docs were the root cause of 23x read:file_not_found, 71x edit:not_read_first,
32x edit:edit_stale_read, and 66x bash:other errors in AI assistant sessions.

.ai-workflows/feature-development.md

@@ -27,7 +27,6 @@ When implementing a new feature:
 - Add appropriate comments
 - Consider performance implications
 - Maintain backward compatibility
-- Review reference plugins in the `reference-plugins/` directory for inspiration and best practices
 
 ### 3. Update Documentation