chore: catch up Storybook preview, coverage, and story hygiene

Stories were throwing without AuthModal/CreateFlow providers, autodocs was a no-op, and several DS/create-flow screens had no stories.

package.json

@@ -17,9 +17,7 @@
     "lint": "eslint . --ext .js,.jsx,.ts,.tsx --max-warnings 9999",
     "postinstall": "npm rebuild lightningcss && prisma generate",
     "storybook": "storybook dev -p 6006",
-    "storybook:github": "STORYBOOK_BASE_PATH=true storybook dev -p 6006",
     "storybook:build": "storybook build",
-    "storybook:build:github": "STORYBOOK_BASE_PATH=true storybook build",
     "knip": "knip --include files,exports --exclude duplicates",
     "test": "vitest run --coverage",
     "test:watch": "vitest",
@@ -69,6 +67,7 @@
     "@lhci/cli": "^0.15.1",
     "@playwright/test": "^1.55.0",
     "@storybook/addon-a11y": "^10.2.0",
+    "@storybook/addon-docs": "^10.2.0",
     "@storybook/nextjs": "^10.2.0",
     "@storybook/react": "^10.2.0",
     "@svgr/webpack": "^8.1.0",