fix(sb10): rename register.js → manager.js for local addons, point main.mjs at folders
Storybook 10's preset loader tries to import() any addon path that doesn't end
in "preset" as a Node.js module. The custom-addons register.js files contain
JSX and cannot be parsed by Node.js, causing CriticalPresetLoadError on startup.
Fix: rename each register.js to manager.js so Storybook's resolveAddonName()
finds a *manager* file and returns type:"virtual" with managerEntries — meaning
Parcel bundles the file rather than Node.js importing it directly. Update
main.mjs to reference the addon directories instead of the register.js paths.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>