fix(folders): return orphaned documents in root folder view

[naaa760]

fix: #15622

What?

• Media with no folder (orphaned items) do not appear in the "By Folder" view.

Why?

• At root, getFolderData only returned subfolders and always set documents: [].

How?

• At root, when collectionSlug is set, we also load orphaned documents from that collection with getOrphanedDocs and return them with the subfolders.

[github-actions]

Pull Request titles must follow the Conventional Commits specification and have valid scopes.

Unknown scope "folders" found in pull request title "fix(folders): return orphaned documents in root folder view". Scope must match one of: cpa, claude, db-*, db-d1-sqlite, db-mongodb, db-postgres, db-vercel-postgres, db-sqlite, db-d1-sqlite, drizzle, email-*, email-nodemailer, email-resend, eslint, graphql, kv, kv-redis, live-preview, live-preview-react, live-preview-vue, next, payload-cloud, plugin-cloud, plugin-cloud-storage, plugin-ecommerce, plugin-form-builder, plugin-import-export, plugin-mcp, plugin-multi-tenant, plugin-nested-docs, plugin-redirects, plugin-search, plugin-sentry, plugin-seo, plugin-stripe, richtext-*, richtext-lexical, richtext-slate, sdk, storage-*, storage-azure, storage-gcs, storage-r2, storage-uploadthing, storage-vercel-blob, storage-s3, translations, ui, templates, examples(/(\w|-)+)?, deps.

feat(ui): add Button component
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