Bonsai Site Snags

fix: prevent CPT capability alias from hiding wp-admin menu items; fix invisible popover text

• includes/class-site-snags-cpt.php: stop mapping singular meta-cap keys
  (edit_post/read_post/delete_post) to SITE_SNAGS_CAP, which WordPress core
  registers as a global capability alias, silently rerouting unrelated
  manage_options checks site-wide and corrupting the admin menu
• site-snags.php: instantiate Site_Snags_Settings so its Settings submenu
  actually registers
• assets/css/site-snags.css: give the note popover textarea an explicit
  color so host theme textarea styles can't render it invisible